Black and grey clothes can usually be washed together. If grey is washed with black, it may pick up some of the black’s color, but only if a lot of the black’s dye leaks out.
Most of the time, you can wash black and dark grey clothes together. Even if the dye seeps out of the black fabric, the dark grey fabric probably won’t change enough for anyone to notice. Because it is darker, any dye that leaks out of the dark grey fabric will not affect the black fabric.
Depending on how dark or light your gray is, you may need to wash it out. It’s fine to wash dark grey clothes with black clothes. Light grays should be sorted and washed with other pastel or light-colored items.
Sorting your clothes before you wash them will make it less likely that they will fade or run when they are washed and dried. Put pastel colors in one group, then separate red, orange, and yellow items from darker green, blue, or purple ones. For the first few washes, wash your new brights separately from your other clothes so that the color doesn’t run onto them.
You can wash clothes of any color together as long as they don’t run or they are old. But things aren’t always that easy. If you don’t clean it right, even colorfast fabric can leak color. There may still be dye stains on old clothes that make the color run. It depends on the type of fabric and the color of the dye.