Like the battery entity state colours can we have temperature and/or humidity state colours?
Battery_level can be 0…100%: 15% is a little, 90% is high.
Temperatures can be different: 35 deg of air (hot) - not same as 35 deg of CPU (cold).
An easy way to define hot and cold for a temperature sensor would suffice. HA would then choose a color gradient for the values in between.
then it should be done per-entity, not per-device_class.