Computers make yellow with red + green..
Btw the three colour channels, red, green, blue each have 8 bits, 2^8 = 256. And for all three channels there are 256 x 256 x 256 = 16,777,216 permutations of possible colours.
If you have a Mac you can use Colour Picker (in Applications/Utilities) to hover over your screen and see the channel mixes of colours under the cursor.
I don’t really know about the sound, but I’d go for something metal, just for durability..
Whatever you go for, it’s worth having a look at the mods you can do to wahs to change the sound, if it’s not quite what you need. Even if you don’t want to do anything electrical you can change the sound by removing the toothed rack and turning the pot dial a little.
FWIW I’m pretty happy with my Vox v847.