Between ROS0 levels 180-199 and ROS1 levels 190-210 on Hex, I got zero coloured shape pieces. Plenty of coloured crystals, but no coloured shape pieces. I'm not sure when it started, but once I noticed I started counting. ROS0 level 200 had 2 coloured pieces.
The early ROS levels did not have this issue. It appears to have started significantly into the ROS generation.
According to Loupau 38, each piece of ROS in hex should have about a 15% chance of being coloured. With a couple of back of the envelope calculations and assuming all pieces are equally likely, that puts it at a little less than 10% chance that any given 4-layer random shape should be all-uncoloured. So 10, 20, even 30 in a row is not astronomically unlikely, but it definitely seems like it's worth reporting.