According to the Canadian flax growers association, dark and light seeds are nutritionally the same. When I sold them, a few customers had personal stories claiming that the golden made a difference.
I use them in a daily drink, grinding them in week-supply batches and keeping it in the freezer.

Grind flax seeds to sprinkle over salads, put in smoothies, over soups wherever you can. Grind them ahead and store them in your freezer.

The darker flax seed has a bit more omega 3 in it than the golden one. Note that the actual benefit may be slight for most folks as the body does not digest the seeds very well and the most often simply pass through undigested. Crushing the seeds just before use in cooking will release the oils that are the benefit to us. Likewise, flax seed oil is good for you but note it goes very fast and that is why it is sold in the refrigerator section of your market and should be kept in the fridge until expiry date.