I want to paint a viarty of metal sheets with a colour hint to it. So for example if I wanted some metal to be distingtibly green, but still has a metallic feel to it, how would I do it? Same thing goes with Khaki and Grey.
Any thoughts?

If I understand well, you're trying to get metallic colorpaints such as we see on most real-life cars? Right?

If so, you could try mixing up small amounts of ink or paint into boltgun metal / chainmail / mithril silver or other metallic paints to get the color you want...
or, something I tried some time ago on some robes of Celeborn, paint it as usual and end up giving the entire surface a thin layer (like a half transparent coat) of the metal-paints.

I'm not sure if this would help you getting the result you want, but it might work a bit.

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Most of the paints I use are by Testors, which (being intended for model cars and airplanes) provides me with a wide range of metallic paints in various colors.
If I didn't have access to them, I'd be doing exactly what BB suggested, though. I've made one or two custom metallics through the mixing process he suggested; and if you're careful to make the layer ultra thin, the transparency method he suggested is absolutely beautiful.

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Thanks! I'll give it a go.