Brown flax seed may be more commonly found than golden, as more brown than golden flax seed is grown commercially. It is most likely solin seed, a crop developed from flax. Solin seeds do NOT provide the same nutritional benefit of flax seeds. Thus, the important omega-3 advantage of flax is missing in solin. You can store clean, dry, good quality whole flax seed at room temperature for up to a year.
Some people keep a jar of flax seed handy on their kitchen counter.
All vegetable oil products require some care in handling and storing. Once you grind flax seed, there is greater risk of it developing an off-flavour and taste. That's why it's best to grind whole flax seed as you need it. This ensures its freshness. After grinding, you should refrigerate it in an airtight, opaque container.