Red: coper, common
Grey: silver, uncommon
Orange: gold, rare

As for an overall strategy tip.. well, first you should focus NOT on winning battles, but on evolving your first cards
(if you can win one or two matchs it doesn't hurt either).
Then as your cards will evolves, they will be much stronger, ability will be unlock (for some of the cards), and you'll
be able to create various deck strategies (focus on offensive, defensive, blockers, tanks etc..)
A good way to start is also to look at "Master's Tips" on the left, wich has been written by some our oldests players.
You can also join the Yahoo group of CitizenKane wich seems very active
Finally, joining a guild might be a good idea to get deeper into the game.

You got some very useful cards in your collection (when maxed out) Chloe is a strong card with also a nice ability to
use as a defenser, Mojo got a nice drain ability to suck your opponent's life.. No Nam is a very good attacker as well..
But again, it's up to you