why does WordPress custom css convert alpha to hex values?

if i’m not mistaken, not all browsers are 100% compatible with RGB color codes, so it might be happening in an effort to maximize cross-browser uniformity of appearance.

this could also be done to facilitate transparency effects, which might be in another option field for Jetpack. there’s definitely less browser support for the extended hex use for alpha transparency, VS rgb transparency.

since extra commas and “px” characters are being stripped out as well, it could be happening in an effort to reduce code size. there may be an option for “optimizing files” somewhere you have enabled.

i’m sorry i can not suggest a work-around, i don’t use Jetpack.