Use only semi transparent colors that look acceptable on a light or dark background about hello-theme

[arielk]

@vovkasolovev Do you have any example how to convert those colors to HEX 8-digits or to RGBA?

[vovkasolovev]

FF-%% = opacity for #000 or 80-%%/2 = opacity for #808080, where %% is two digits from original #%%%%%% gray.
But This shouldn't be done by math, because mid gray should be tweaked to be more white and with alpha transparency to be acceptable to work for eyes on any background. This task should be done by designer.