Hi Blake. Don't mean to sound facetious but what exactly are you looking for?
For the most part the written historical sources for this period are silent regarding the colours of units. Much of what we know regarding appearance come from art especially pottery which, generally speaking, is concerned with depicting a particular subject matter, perhaps a well known historical figure or something from the realm of myth. In a nutshell, there are no uniform guides for this period.
Having said that, one can likely conclude that units in professional armies such as the Macedonians would have more uniformity than those raised from citizen levies. There is also some evidence that units of the Royal Persian Army may have worn uniform colours.
In my armies for the Diadochi, each phalangite unit has a particular tunic colour and shield design. Tunic colours are varied in mercenary and citizen units with the latter sometimes sharing a common shield design.
You can't really go wrong when painting armies for this period. Just keep in mind that many modern colours would have been unavailable and that the price of purple would have put it beyond the reach of most. Colours would be rather subdued and would be limited to those found in nature; red, brown, green, black, blue, yellow etc.
There are literally hundreds of pictures of Hellanistic wargames armies available on the web. Try a google search and you will find lots of inspiration.