Apparently colourless too: https://chemistry.stackexchange.com/questions/31587/are-there-any-known-chemical-properties-of-tritium-water-that-make-it-unusually h

Apparently colourless too: https://chemistry.stackexchange.com/questions/31587/are-there-any-known-chemical-properties-of-tritium-water-that-make-it-unusually https://chemistry.stackexchange.com/questions/31587/are-ther... Some other neat things I found along the way, mostly on Wikipedia: heavy waters freeze at 4-5 degrees Celsius, the heavier the higher. Frozen heavy water will sink in liquid normal water, and pure "tritiated water" ("super-heavy" water, with tritium hydrogen isotopes) is radioactive and will boil itself if pure enough.