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Apply a light base colour, in this case I use R22 "Prawn Red"
Try to use an even lighter colour for the red colour to displace some of it and create the highlights.
Now get darker, work with a dark red or violet to make the shadows. Blur the edges with the base colour by wiping them.
Define the higlights again with your light colours. Here I use v0000 and the blender.
Again, do some shadows with a darker colour. It's up to you if you use one that is darker or the same colour you've used before.
Again: Lighter colours for the highlights. You should do this often, because you can take away more colour every time.
To define the edges, you should use a dark colour and clean up the areas where the light colour shouldn't be.
Now for the eyes: Use some grey to make the white part of the eye more realistic :) I usually use C1 and C3 to create a light gradient.
Work with the blender to get a lighter tone of red and create a base. Then, apply the original colour for the pupil :D