It's hard to see them clearly enough, but most of them appear to be aphids, which can be nuisance pests (not serious) of indoor and outdoor plants. Aphids can be many colors, depending on species and what plant they are feeding on; black, yellow, green, gray, and pinkish-rose are common colors. If found on a plant, most aphids can be easily squished or sprayed off with a garden hose (or sink faucet sprayer) using plain water.

Miri