By true RGB, I meant thousands of colors, and not just three. I've seen the eBay 5mm LEDs, and a lot of them simply switch between 3 colors, and ONLY those 3 colors. I think Mayhems are ALL glycol based coolants, but I'm not sure, as I don't use colored coolant. I prefer colored tube. But check out this link: http://sevierlab.vet.cornell.edu/resources/Chemical-Resistance-Chart-Detail.pdf If you check that link, find the PETG column, then scroll down to "ethelyne glycol". At 20 degrees C, it says "some effect after 7 days of exposure". At 50 degrees C, it says "immediate damage may occur. Not recommended for continuous use". Sounds pretty scary to me, so I'd stick to acrylic tubing. From what I read, acrylic tube is more "glass like", where PETG is a bit more opaque, so acrylic will show off the coolant better, even though it's trickier to work with. DISCLAIMER: I'm only regurgitating other people's info, as I haven't done hard tube myself yet. I have NO personal experience with this stuff. But from what I'm reading, PETG tube is cheap stuff that really isn't suitable for water cooling (since most of us use glycol based coolants or additives.