Either thats the color purple you have got or its not mixed right so theres not even purple pigments or your color under it is lighter (perhaps white) so the lighter color under the purple is effecting the color if the purple.its like putting red paint ontop of white you end up with pink.you either have wrong color or you need to apply more purple to get the correct color.
In reply to - Heen posted an update in the group Intermediate Modeler – Modeling Competition 2013 So i have painted the inner frame in gun metal, and partially put on some armor. Still dont know why the purple looks pinkish