You have a few choices, but the most economical and nutritional one is as follows:
Buy whole flax seeds at the health food store. They'll last for an indefinite, long time if you buy them whole and keep them in the fridge. If you don't already have a coffee grinder, you can buy a small one by Black & Decker for about $13.95 at Kmart or a place like it. You MUST grind the flax seeds to get any nutritional benefit from them. The whole seeds will pass right through you. Each day, grind 1-2 TBSP (someone correct me if my quantitiy is wrong), and eat it however you'd like. Some suggestions are to add it to cold cereal, add it to oatmeal after you've cooked it, mix it into a nut butter for a sandwich, add it to smoothies, and so on. The Omega 3's break down under high heat, so it's recommended that you don't cook with them, but there's a debate as to whether or not it's safe to bake with them.
Also, the color of the seeds doesn't matter.
I hope this helps!