YOu might try experimenting with metallics, a mix of boltgun or the darker equivalent and then silver, then wash with purple wash or ink over the top.
I'm not a big fan of red with purple, tends to look off, and the darker the red the more off it looks. If you really want purple to look good, use a linen type of cloth fabirc, with shades of warm orange yellow or tan to help with the contrast.
What would be interesting, if oyu want red and purple, is to try and use Vallejo Red Violet, its a great color and have a nice mix of red and purple, it almost a plum color.
Anoyther thing you could try if you feel like experimenting a bit is to use "interference" colors. Liquitex makes a tubes of artists acrylics, and I remeber they had a color called interference violet. Its a clear paint, but when thinned and applied on top of your existing color, it has a pearl or metallic purple sheen in the light. its not the easiest thing to use, but it does yield some neat results once you get the hang of it.
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