Temperature overlay missing and/or not changing colour

[allmhuran]

I was playing around with some parts and noticed that when they increased in temperature their overlay wasn't changing colour (from red to yellow to bright yellow), they just stayed a constant red. The debug thermal info showed that their actual temperatures were increasing as expected.

So, I built a little "test rig" with some physicsless target parts (cubic struts, landing gear) to see if maybe this was a change in 1.05, that perhaps physicsless parts didn't change colour anymore. Below is a screenshot of the result. Anyone had this before? All of the parts used in the pictured craft are stock.