I could be mistaken, but I believe there's currently an issue with the way LibBars-1.0 recycles its bar frames. This became apparent once barPrototype:SetColorAt was implemented.
I used this new method to set my bars to the corresponding RAID_CLASS_COLOR value, which worked fine, but then once another LibBars-based addon, Hourglass, created a new bar, it would have the same color as the last bar of mine that expired.
Attached is an example using my addon, RaidCooldowns, and the example addon FlashFrames. I ran RaidCooldown's test function, waited for a few to expire, and then re-added more bars to FlashFrames. As you can see, bars 4 and 6 used both the color and the font from RaidCooldowns.
I'm not sure if this is a bug in LibBars or if it's working as intended and thus the responsibility of any addon using the library to reset the color and font of every bar it creates.