Colours are always a tricky thing. I based all my GNW uniform colours on a visit I made to the Army Museum in Stockholm about 18 months ago.
Pikes seemed to vary in colour but I never saw white ones. Old wood turns a dull pale grey but I suspect this was a trick of the light. I tend to go for a pale woody (!) brown or sometimes a yellowy colour. The key thing, from observing ECW reenactors is that all the pike shafts were different colours depending on the wood and the age of the wood used. Pikes had to be made of strong wood and Ash was often used which is a yellow wood.
The Army Museum has some reproductions of GNW uniforms as seen below. The flash actually makes it seem darker than it was in reality.
Below is a genuine Swedish uniform coat from the slightly later period of 1756 but this is what I have based my colours on. The colour reproduction in this is spot on. My painted figures are all photographed in flash and so have a slightly turquoise cast that isn't there is real life.
The yellow cuffs etc are very pale, as you would expect from natural dyes, not the bright yelllow some people use.
As regards the buff equipment it should be...buff.
Again these uniforms are reproductions but the buff leather equipment is not that different in shade from the yellow facings.
Always interested to hear from people who know more, of course...