I agree. This was the anti-icing paste used in this period, a not that successful method of trying to prevent or minimise icing, before the introduction of the electrically heated, pulsating de-icer 'boots'.
From what I've seen in the few, genuine colour photos of both Halifax and Wellington aircraft, this was more of a faded, yellow / sandy colour, and was applied by brush ( normally a broom ! ), and not always very neat.
I used to have a superb photo of this paste being applied, which looked a messy job, but it was in a book I loaned out years ago, and never got back.
I'm not sure if it was applied to tail-planes, but logic would suggest it probably was.
BTW, is that you Derek ?