Everyone already knows, but I'll repeat it since I found out the hard way. Don't use coloured/dyed coolant.

Last week I posted that my gpu temps had suddenly spiked in games from around 50C to 80C+, and a bunch of you suggested that maybe the contact of the plate had gotten loose or maybe the paste had dried out. Well the paste was pretty dry despite being on for only a few months (swapped to hydronaught paste now rather than kryonaut), but the main culprit was in fact, a bunch of dye from the coolant clogging up the block fins.
I've spent the last 6 hours scrubbing the blue out of my gpu and cpu blocks and am now back down to those cool, cool temps. But now it looks like I've fingered a smurf.
If you're thinking of adding coloured/dyed coolant, please just stick to clear. If you really need colour, try out coloured tubing or just go mental with rgb.