The Old Ruminator said:
Can Miliputt be coloured during mixing or afterwards to last in a cave environment.
I have never used it (although it sounds like something to keep handy)
From their website:
"Colouring Milliput
There are a number of ways of colouring Milliput.
Different colours can be obtain by cross-mixing or blending from the range of colours that Milliput is available in.
Powder pigment can be mixed in, in small quantities, so that the mixture does not become too dry and crumbly. Strong powder pigment rather than powder paint is better as smaller amounts can be used.
Liquid colourings, like enamel paints, oil paints, spirit based-dyes or pigments can also be used to colour Milliput, but liquids or pastes may be difficult to introduce into the putty, again small quantities should be used, to avoid creating a very wet mix that may be difficult to mix.
In all cases the Milliput should be thoroughly mixed by rolling & folding about 30-35 times."
They don't say if the colours will last, but if it sets hard I imagine they will stay there.