They're looking good so far

, though some quick feedback for ya:
The tanks look a little grainy, which is probably due to dry brushing. You might want to pick out details and add some contrast, like the jerry cans and the rope on the tops could be painted another color to add realism. Same with your searchlights, plasma gun coils, etc on your bikes. Weathering would also help your tanks a lot once you've hit the details.
As far as the silver color, it looks like you're using mithril silver. You might want to base coat with boltgun metal, then wash it with badab black and then work up a layer of 50/50 boltgun/mithril before using the pure mithril. It will help to add a smooth transition of depth and still give you a bright metallic look.
You might want to water you paints down a little as well and use multiple coats to get good coverage. This will help you get good crisp color and help keep your details sharp.
Overall I think you've got an excellent start to an army. Keep painting and you'll be amazed how fast you improve.