It's always best to separate white and colored clothes to wash them, but that can leave you wondering if you can dry them all together. The short answer is:
It might seem alright to dry everything together, but it's not, primarily because of colorfastness or color bleeding. Even slightly damp dark or colored clothes can transfer dye to white or pale-colored articles in the dryer, just as they might in a washing machine -- even if they've been washed a few times already.
Because of Dyes
Some dyes -- those used in dark blue jeans or brightly colored new towels, for instance -- can leach for several washes, distributing color to any white or lighter-colored clothes they touch as they tumble together in the dryer.
Another reason to separate some clothes from others in the washer and dryer is to avoid damage. A zippered winter coat or heavy wet jeans, for example, can act as a laundry bully, roughing up or possibly damaging lighter weight items, such as blouses or delicate lingerie. Hanging light clothes to dry -- especially if the care tag instructs to do so -- solves both the damage and dye issues.
Better Safe Than Sorry
To be safe, always , so you don't end up with tinged, torn or tattered white -- or colored -- shirts, pants, skirts or sheets.