Often seed (any sort) that is not its natural color has been treated in some way.
Perhaps a fungicide to help the seedlings resist diseases while they sprout.
Perhaps a pesticide, and this seed is intended to be used as bait to kill gophers.
I thought Bermuda grass seed was a lot smaller than that. Maybe Tall Fescue seed? That one is about a cm long.
Here is a link to a picture of Bermuda grass seed with a scale. See how the seeds are not even 5mm long? Maybe they are just 2mm long.
I think you can figure out germination time faster simply by sprouting some. Put several dozen in a cell pac or 4" pot and keep it moist, not soggy wet, and about room temperature. In a bright window would be good. Barely cover the seeds.