Can a CC05Y or CC10Y be used for a warm up filter?

I'm just curious. I mean, yellow is the opposite of blue.

I have always used a CC 05R or CC 10R filter. Great for those overcast days.

Depends on what you mean by warming. And not all films are the same. You've also potentially got secondary issues like UV sensitivity. But
in generic rather than specific application terms, a skylight filter is typically a very pale salmon color (magenta with a tad of yellow), and a
properly made 81A warming filter is slightly amber with a pinch of pink, rather than yellow per se. This increases in intensity as you go up the
scale of the 81 series. A good filter manufacturer will test results with various specific films before advertising their recommendation. You should also do specific tests if you want optimum results. CC filters are really for a different range of applications. If you can find a copy of the old Kodak filter guidebook with all the specific spectrograms and descriptions in it, it is a very valuable resource into traditional filters.
Some of these newer multicoated filters are best learned from reputable manufacturer's site published information. But in the long run, you
just need to test under relevant conditions.

I found a 55mm CC10Y on Ebay for $6. So I get to try it out. I'll look for a cheap CC05R or CC10R now.

The filter came in today. I took a few quick ones with the digital for instant results. The results are quite nice-better than I expected. Since Velvia 100 is a little to the magenta side, a typical warm up filter can put it over the top with magenta. So this CC10Y may be a better option. When I shoot a roll of Velvia, I'll do a comparison with and without it. Here are the results with the Nikon D300 and "flash" white balance a few minutes after sunset.