I know this is a few months old, however, I was researching this very thing today and came across your thread.
The only way I can image we go about colored fonts per temp color would be to create an outlined font with a colored temp bar behind it, hidden as part of the background image, if you're using one. The only trouble would be the changing numeric value of the temp - it'd be difficult to create the range of values involved in a transparent, block-like font that would still display the bar behind it and not mess up your background.
While it is possible, I suppose, I may just stick to a small dot-like indicator (think bullet-style list) next to each value.
If I come up with anything, I'll update this thread.