Exploring the trope of symbolic/semiotic rendering of swearing:

TTAB 12-4-13

Taking my cue from the phrase ‘turning the air blue’, the rest fell into place pretty quickly; it was a nice excuse to return to ink-brush rendering. Of the symbols the latter three (hash, exclamation, lambda) seem to work better than the asterisk and the spiral.

It’s interesting to note that in symbolic swearing there doesn’t seem to be a massive pool of symbols from which they’re typically sourced; it’s usually along the lines of those shown above. I probably should have gone for a more outlandish set, possibly incorporating the following: an interrobang; a biohazard symbol; an alto clef; and the Eye of Horus.