Low water clouds depict in ochre colours in the Night Microphysics RGB. While the BTD (IR12.0 - IR10.8) responsible for the red colour beam is slightly positive on a scale reaching from -4 (dark) to +2 degrees (intensive red), the green colour beam shows positive BTD and hence also a strong contribution. The blue colour beam is also contributing but less.
The green colour beam is of varying intensity depending on the thickness of the low cloud layer. The thinner the layer, the smaller the green contribution which makes the colour turn into red (see image below: green arrow).
When low water clouds are warmer (e.g. over the sea) then the colours turns into blue as the blue colour beam gains intensity.