If you dye or paint intarsia it is known as segmentation and is how I do most of mine. I have used oil base stains, acrylic paints and aniline dyes. I decided to color the pieces after doing intarsia for a couple of years and many of the pieces darkened to shades of brown. This is typical of most woods when exposed to sunlight. This can be delayed using some finishes with uv preventive properties, but they will still darken eventually. How you want to make them is entirely up to you. By painting or dyeing the wood, you do not have to select only woods that have a particular color. I generally select woods that are as white as I can find. usually aspen, poplar or soft maple.