Currently, transparency doesn't work with hex codes, relevant part of README:

Transparency Mode
Press t to toggle Transparency Slider. While this mode is active, you will only be able to output the color as rgba() or hsla(). If you want to output as HEX, press t to get out of Transparency Mode, and you'll be able to press o to output your color as HEX.

Could it be possible for this to also work with hex? (because exiting transparency mode of course loses the transparency info)
It's pretty standard for the transparency value to be at the back of the hexcode, going from 00 to FF. (I know there are outliers, but I would rather have a way to add transparency then no way at all).