They need to add heater packs underneath and thermocouple readings. While white is good at rejecting external thermal radiation, it is also poor at emitting thermal radiation. A white surface can be hard to keep cool if the heat comes from within. In particular, white will look like it has a much better comparitive advantage when imaged in IR than is likely to be the case in real usage conditions.

Yellow, red, and gray may be more comfortable in practice.