Jerry, it may be that the colour difference is due to whether the rice is hulled and polished (the white colour) or not (the darker colour).
Either that or the darker colour may be because the rice has maybe gone off!
Arguable, the whiter it is the "better" it is (or at least the more expensive it is) since you're no doubt paying for the extra processing involved in getting it white.
I understand that a couple of years aging (up to maybe ten years) is pretty normal.
Basmati rice is also a "long-grained" rice (opposed to "medium-grained" or "short-grained").
The best basmati allegedly comes from the foothills of the Himalayas (where the unique climate allegedly best suits it's growth).
You should probably look for a basmati rice that is:
- From the foothills of the Himalayas (often of Pakistani origin)
- Has uniform, unbroken grains and no grit, residual husks, etc
- Has some reputable seal of quality approval
- Basmati from "Dehra Dun" is purportedly the best basmati of all
Like most things in life, you get what you pay for.