Keith,
Very nice. Clean, crisp detail excellent craftsmanship. You picked two of the most difficult colors in the spectrum to highlight and shadow! I was taught that the key to these colors is that there really is no major highlight but as Guy pointed out, it's all in the shadows. If you try to highlight blue, it turns to sky blue and ends up looking like faded denim. Red turns pink or orange. If however you darken the shadows and paint the base colors a much darker shade, then you generally get the desired effect. For example (simplified versions, you can use different colors, I'm just illustrating the point)-
Prussian Blue-
Black shadow
Indigo mid tone
Prussian Blue highlight
Red-
Dark Violet (like Mars violet) shadow
Deep red mid tone
Cad red highlight
Cad Scarlet extreme highlight (if a scarlet uniform)
The goal is to use the color you are trying to portray as the highlight. The depth of the shadows will make the color look more natural at the highlight. The same method can be used for white and green.
That said, I would change anything on your bust, it is beautifully done. Chin scales are the straps from the chapzka (sp?) that tie under the chin.
Great stuff!
Lou
PS the face is awesome!