At the commencement of WWI, the British were using a grey officially termed Battleship Grey. This was very dark, almost a charcoal grey, and can be easily spotted in early photographs.
During the first year, however, this was changed to Mid Grey - partly because of the shortage of dark pigments, and the realisation that shortages might get worse as the war went on. The new shade proved better.
In the mid-war period, many battlecruisers had a panel of dark grey or dark blue amidships on the hull. This did not reach to the bow or stern, the length being usually from fore-turret to aft-turret. It was intended to give a 'shortening' effect when viewed at a long distance, to confuse the enemy as to range.
New Zealand had a white ensign painted on both sides of her foretop.
Black waterlines were discontinued in some areas, although major units with the Grand Fleet usually continued the practice.
Torpedo boats and destroyers were usually black for early classes, but dark grey for newer vessels. Units of the 'L' class entered service in black, but soon changed to grey. War-built units usually completed in Mid Grey. By 1917, nearly all destroyers and smaller were grey. Only a few torpedo boats continued in black until the war's end.
On 'Tiddly ships' (Fancy) the practice of painting the metal areas around the anchor cables in Brunswick Green was continued, and most turret-tops were in dark, flat Brunswick Green on capital ships. Some may have used dark grey.
After Jutland, the idea was adopted of painting some turrets of battleships and battlecruisers very dark grey. These were then marked with white calibration marks so that other ships could see the direction the guns were trained, even if unable to see the target themselves. Which turrets were painted this way was deliberately varied from ship to ship in all classes, which helped within the squadron when identifying units in low visibility. The placing of aircraft flying-off platforms was similarly varied.
Cortesine was a mid-brown linoleum-type decking used on small ships in areas where the crew required a good foot grip, but timber would have been too heavy. Cortesine was also used on larger ships as an alternative to wood on high areas, such as the bridge and bridge wings, where men had to stand for long hours on watch. This was to protect their feet from the cold of metal decks. Strips of cortesine often ran along the decks of some ships, particularly to torpedo tubes and etc. These formed an impression of footpaths running along the deck. Unlike other nations, there is no evidence that the metal strips holding these down were polished.
On older ships that used coal, it was the custom to paint the horizontal metal decks directly around the funnels black. This was discontinued on oil-burning ships. Those with grey decks normally had the horizontal surfaces in a darker shade.
Wooden decks were 'holystoned' daily, and took on a very whitish colour on British ships. Holystoning consists of virtually 'sandpapering' the wood fresh each day, with special stones. The task was hated by crews, and they were delighted when - in smaller ships, such as cruisers that spent a lot of time at sea - the practice was discontinued for the period of hostilities. It continued on capital ships, partly to give the crew something to do in a very boring daily routine.
British capital ships often carried triangular black/grey metal or canvas sections projecting between the funnels and from masts. This was intended to confuse German range finders, as it was thought they used a similar system to the British. (They did not.)
British ships had carried an extensive system of coloured bands on their funnels pre-WWI, and this was continued during the period between the wars. However, it was not widely used during either war. Destroyer leaders sometimes did have a black or red band on their fore funnels to help identify them from other units in a flotilla, but the practice was not used for ships larger than destroyers.
Canvas was painted grey in home waters, using the same paint as the rest of the ship. Because of the nature of the material it took on a slightly lighter appearance than when used on metal. The canvas on ships boats appears to have remained mostly white or a pale grey. On the Mediterranean station, it was common for canvas to be painted white for British major ships, and many other pre-war practices to be continued.
The official over-all colour for the Mediterranean was the same Mid Grey as the Home Fleet. However, in some notable cases this was modified into a camouflage by applying light grey or white over it. The Dardanelles is a good example of this. It was usually confined to up-and-down lines of pale over dark, on funnels and upper works. The same style was applied to the Invincible at the Battle of the Falklands. False bow waves were also more common in the Mediterranean than with the Home Fleet.
Hull pennant numbers on smaller ships were changed from time to time to confuse the enemy. They varied from white to red or black. Toward the end of the war, there were so many ships in service that the practice of changing them was discontinued. (It was confusing their own side.)
When the British adopted camouflage schemes, it was not intended to hide the vessel, but to confuse the viewer as to its direction of heading, speed, etc. For this reason, black-and-white stripes, chevrons or checks might be used, sloping in different directions - all on the same ship! The variety of colours changed according to the camouflage design. Light cruisers used on patrol duty in the North Sea were painted in lighter colours because of the notoriously varied visibility and fog. HMS Forward was painted in a mixture of sea-sick-green, pale mauve, grey, black, and white in a 'crazy quilt' or 'dazzle' style.
Only a few British destroyers were painted in this fashion. The practice where it did occur seems to be limited to convoy escorts, particularly Flower-class sloops and other late-war types.
Experiments were carried out early in the war to try to conceal ships. It was decided fairly quickly that the varying light conditions a ship could experience from day to day, hour to hour, meant that no scheme could suit all. The only reasonably successful schemes, such as the American Mackay style, were most effective in dull conditions, over 8,000 yards. In these conditions, the ship could indeed be hard to see. However, if the ship was that far away, it was already safe from submarine attack.
The danger zone for U-Boat attack was less than 6,000 yards. At such a range, it was impossible to hide a ship on the open sea. Therefore, if the ship could not be hidden, then the next best thing was to confuse its appearance and deny submarines the chance to easily determine its course and speed. Therefore, while many WWI dazzle schemes may appear to make the ship more visible and be of quite lurid designs, it must be kept in mind 'why' they were painted that way.
Dazzle was extensively used in the Atlantic. Due to the huge shipping losses of 1917, orders were issued for all merchant ships to be painted in 'crazy quilt' or 'dazzle' camouflage. This was carried out from very small ships to the largest liners. It was also carried over to seaplane carriers with the Grand Fleet and other auxiliary vessels, convoy escort sloops, etc.
Atlantic-type dazzle camouflage does not seem to have been as commonly used in the Mediterranean, partly because brighter conditions made it harder to achieve the desired results. However, monitors on duty in the Aegean area were often painted earth brown or khaki. This made them hard to see against the coast, if being attacked by a U-Boat approaching from seaward.
Submarines went through various schemes, starting with black. They later tried dark grey, dark green, mid-grey and pale grey. Two Royal Sovereign-class battleships were camouflaged - one fully, and one only from the hull up. It must be remembered that WWI camouflage schemes were intended to confuse enemy submarines as to the course and direction of the ship. It had been decided it was impossible to actually hide a ship from observation. Hence, bright patterns and colours abound often in check-and-stripe combinations.
Commonwealth countries used the same schemes as the British fleet. However, most Australian destroyers appear to have mid-grey hulls, and light grey upperworks.