These guys should be pretty easy to paint given they are mostly silver. You can even get metallic spray paints (plastikote makes a few - you can get them in B&Q, Wilkos, etc).
Once you have selected your base colour, paint all the plates etc silver, paint the trim a dark grey, then wash with slightly thinned badab black wash (or whatever the current black wash is called), and then go over the trim again with a thick wash so that it has a nice shaded black colour.
You can then use one of the foundation yellows to paint the hazard stripes, going over it again with something like golden yellow.
Remember to thin both these paints slightly (most easily done with water) so you don't have huge thick paint brush streaks in your yellow.
You can then pick out any other trim etc (the joints in the armour for example) in whatever colours you want, or do that first after spraying silver so you shade them with the black wash.
If you want any tutorials on any aspect of painting, check out
this site.
