There's a standard? (/sincere)
Viewing post in Psychoballistica: PROJECT RETURN FIRE comments
An unofficial standard as far as having the symbols printed commercially in color, at least; it's understood that adding color to the cards is a modern twist.
When they do show up in color, the color scheme that shows up on Wikipedia seems to be the most common (with some variations), and the earliest reference of that colorscheme seems to be 2008 on the site itself. So it's likely a case of Wikipedia informing an unofficial commercial standard.
Either way! It'd be interesting to hear the thought process on the symbols' colors and meanings, even if it ends up being not that deep. 'They just felt fitting' can be fascinating in its own right.
Here's what I could reconstruct from notes from two weeks ago me.