Thats a nice choice of colours for those models - but if I was to offer any advice at all I would say that you need some contrast, and some highlights.
Washes are a great way to add depth to a model - simply water down your paints in a darker shade than the colour to be shaded and slap on.
Ok, thats a bit vague, but is essentially the basics of the procedure.
Have a little search on youtube for vid tutorials - most are generally ok.
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