A few years back there were loads of liquids- Woolite did one, Dreft and Persil did one specifically for black clothes.
DH wears alot of black and I use Ariel/Sainsb colour liquid or the wash ball thingies (the non detergent with the little pellets, which are okay but not as thorough at cleaning.
DS's new school uniform is black so I was looking for something to wash it and keep the colour.( And bear in mind he's a 24 carat filth-magnet
)
TIA