There were two colours carried by a battalion until sometime in 1809 I understand – information from a book with a Polish writer whose name I have long since forgotten.
Irlanda, Ultonia and Hibernia all sky blue coats(there is an error in the Men at Arms vol one tables, Osprey, corrected in a later volume). Dark blue was introduced to the army for all regiments but then the sky blue reintroduced before the 1809 war it seems. Vol 1 Osprey guide seems to be the most accessible source of material on this in English.
The regiments were kept at an undermanned peacetime footing , part of Godoy's economies I think, then expanded when the French were taken on. Given that and the collapse of central government in many areas, it seems likely anything was worn until it was no longer serviceable. Blake's army in the autumn of 1809 is described as being in rags. A far cry from my fro-fro battalions of AB 15/18mm Bourbon lovelies!
The Men at Arms series reproduces the 1814 survey mentioned by DN Jackson – this appears in both the original Men at Arms by Otto von Pivka ( aka Digby Smith) and the more recent 3rd volume brought out a few years ago as part of the three volumed Spanish Army study by Rene Chartrand, which must be as good as it gets.
Incidentally, the table indicates Hibernia wore blue, Ultonia sky blue and Irlanda sky blue – some regiments made a point of getting what they want to wear I suppose.