Yellow and purple layered perhaps. Or in a pattern. I like their contrast.
I like decimals more than fractions mostly because I think better in them, but I am fine with using fractions and irrational numbers when appropriate.
The reason I dislike seeing 0 as a number is because from what I can tell, 0 is only a place holder, and treating it like a number leads to inappropriate and impossible expressions like 2/0 equals undefined or infinity.
I dislike negative numbers because they complicate the math system. If you treated -5 simply as a magnitude rather than seeing it as a negative number, then there would be no need for i. I guess that a long time ago people came up with negative numbers for short term convenience, since -5 is a lot simpler of a concept than 5 units theoretical deficit, but it complicates the hell out of trying to find square roots with them, and so half of the whole goddamn number system had to have a new ass backwards counter intuitive set of rules made up for it.
As for WC: I like my color better.