Hi Terry, depending on scale I usually prefer to do veins the blue/green shade they appear, as well as showing their three-dimensionality by highlighting and shading subtly.
It's very common today in smaller scales to see them done purely as a lighting exercise and I've talked about this with other modellers a few times who are of the opinion that at 'scale distance' the veins aren't obviously coloured. But I think on painted figures at 1/32 scale and larger they just don't look right if you're viewing the model closely (more like scars than veins).
Mixing the colour of veins is not easy but I would always recommend you start with your basic flesh colour and add to that the blue or green paint
very cautiously. It is so easy to go too far on this so check the colour against the painted figure regularly! You may find you have to add in a tiny bit more white to compensate for the darkness of the blue or green.
I generally paint the skin to completion without the veins, including adding the shadowing under any prominent ones (paying attention to the direction of light) and then glaze lightly with the vein colour. Sometimes I don't think they then need further highlighting but if I think they look too flat I start with a normal skin highlight and add a little of the basic vein mix.
BTW, if they're not sculpted on the model and you're painting the illusion only, do use your own hands and photographs as reference to the vein patterns! If one makes them up they tend to look stilted
Einion
