Oh yea, the bonus drop (be it blue or red) is still random. But the rate went up with Jack Frost. IIRC, I had a bonus blue drop rate of below 20% for Jack o' Lantern, but shot up to little over 50% starting with Jack Frost. Forgot what my bonus red drop rate was for Jack o' Lantern though.

Funny enough, I've actually gotten the Barong gun to drop once without MVPing!
i.imgur.com/epuON3p.png
I didn't even vice-MVP that one.