this is pretty important.

Today, most kitchen trash bags are white (though the outdoor kind tend to be dark green or black). That stems from a time when most kitchen appliances were white or shades of beige. That time has passed.

...

While stainless steel is the bigger trend in appliances, black is a bigger deal in trash cans, said Lisa Smith, marketing manager for Hefty waste bags, primarily because black cans are less expensive than stainless steel or chrome. Consumers also find black bags look better with stainless steel than white ones, she said.

Delving deeper, Hefty discovered trash also looks better, or at least less messy, in black bags. (via)

now you know everything.