The Canon cameras that I have also have a hard time getting purple correct. In the menu function is the My Color option, choose that and go to custom colors. Here you can change the color palette to suit your tastes with options for saturation, contrast, sharpness, red, blue, green, skin tone. This is outlined on page 87 of the owner's manual. You can also try a different white balance setting to see if you get better results. Just remember if you change the white balance it will stay on that setting until you change it back. This has worked really well for me in getting much truer colors.
About white balance, realize the camera's interpretation of white and through this other colors will depend upon the light source. If you're an artist then likely you are taking pictures indoors. Unless you are using a flash the camera uses ambient light source. Standard tungsten light is more yellow and fluorescent more green. The camera will attempt to automatically detect what is white in your picure and adjust for this, but if there's nothing white in your photo then it has a hard time. It can also have a hard time if you have mixed light sources such as taking a picture in an art gallery where the painting is illuminated with tungsten spotlights but there's a window nearby letting in sunlight. You can manually adjust the white balance for the light source being used or simply whichever produces the best result. If I am in an art museum taking photos (which I always do with flash disabled even if they don't insist upon it) I manually set the camera for the white balance rather than trust the camera to do it.