Maple Burl can be dyed many colors!
The knife on the bottom is Blue Maple Burl, but the dye didn't penetrate the wood as much in some areas as it did in others, so it has blues, purples and pale blue in it:
Box Elder looks similar to Maple burl, but with more eyes and less swirly grain, the one on the right is Blue Box Elder Burl:
2nd from the right is brown Maple Burl:
2 on the left are Black Maple Burl, then natural Pale Maple Burl, then Brown Maple Burl:
Maple Burl is sometimes dyed red, but it may end up looking more pink than red. Dark Purple is another color I have occasionally seen it in, along with green and orange. Box elder Burl seems to be dyed in more colors than I see Maple Burl dyed usually; it may take the dyes better? Redwood Burl also can be dyed. Sometimes the eyes in wood burls do not take the dye and stay a natural color while the other parts of the wood accept the dye, so you get a 2 tone affect. Other times, they mix 2 dyes to get different colors into the block.