You really need to spend some time on Dr. Wayne Coates' website. He calls himself (rightly) "Mr. Chia" and he has done more than anyone to educate consumers about the benefits of chia seeds. He was recently asked about the difference between the two samples of chia seed pictured below.
The seed on the left is clearly inferior quality, contains many immature seeds (brown) and even the black seeds are a lighter color which is not normal. The seed on the right is much higher quality. So look at the seed you buy, brown is bad, white(cream) or black are good.