Skidder's link is spot on (see what I did there?) and those units are excellent. Don't expect to get much use out of the foot controller though ... much easier to set them as fire & forget.
BUT.
That's an extra tripod pole to take up space, extra cables to plug in and trip over, extra stuff to be set up and then broken down later, another large box to fit in the car.
All good if you want that stuff, you play venues with enough space, and the band can deal with the hassle. The Junkyard Dogs uses loads of lighting and we're very happy with what we do, but YMMV.
If you're just dipping your toes in the water, a good place to start is these:
http://www.thomann.de/gb/cameo_flat_par_can_rgb_10.htm
You can mount one each onto your PA poles using:
http://www.electricalcounter.co.uk/products/Lighting/Indoor+Lighting/Intalite+Indoor+Lighting/Track+Lighting/Track+Lighting+Accessories/C-Hook+Clamp+for+SFL+Track+Lighting+Range,+3.5cm+Maximum/3642515555?gclid=Cj0KEQjwyMafBRCU7OCRyc2vitsBEiQAKV4H9ChLw_cJ6FuEXzI7zwxYQWBRaKCzmmMSFQIqeHi6vZsaAu4A8P8HAQ
The whole lot will fit in a small hold-all, you use your existing poles, and the two extra power cables will be in existing cable runs where your speaker cables are running anyway.
By no means the whole solution, but a good start place and also something that extra lighting in the future will complement rather than have to replace.