As a conditioner it's used to remove the final traces of soap, which can make dark things look dull.
Don't ever hang black stuff in the sun here, it'll bleach the colour out horribly!
And as Odile suggests, a yearly re-dye works wonders.
Vinegar can help to 'set' colour, it acts as a mordant. I often rinse dark clothes in a dilute solution of it before the first wash.
Coral color is really good. And Perwoll, black. Only liquid snd all washed 40deg max. Turn your clothes inside out, too. Shirts or fine clothes, use a laundry back to zip it in (it's now available everywhere, I got mine in Tchibo). I never use dryer since it's pita on clothes, line drying seems to preserve fibres and colors well. I wear dark suits and stuff for work, but works the same way for my hipster black clothes, heh. Who actually bothers with dry cleaning here...
No worries Angela, I know that only too well... had a south facing balcony at the previous appartment, the Sun in summer would bleach really attractive pale lines on clothing if left for more than 6 hours out. You need to keep the clothes inside out if you can't remove them in time!
Anyway, where do you get black dye for clothing from? That's an interesting avenue for me.
Most of the larger pharmacies should sell dye, you'll probably need to ask for it as I don't think it'll be just on a shelf.
It's quite possible that the Migros and Co-op have it, Manor certainly does.
The Migros in France also sell it in the household cleaning products section...
As said before, I always buy my Dylon washing machine dye in UK as it is so easily available at all retail stores, like Tesco and Wilkinson, etc, or get friends or relatives to bring over. As I do not dye from pale to dark, but black to black, the weight of the fabric for quantity of dye is not so crucial, as long as you don't overfill the machine so items can move freely. £6.05 at Tesco on line. Here is their video:
The dye sold in the french Migros is Dylon (the newer liquid form, which is way better than the older powered version), not sure about the ones I've bought in CH, but that also dyes well.
About €5 for a box that'll do a kilo of fabric in France, or loads-a-money in CH; I can't remember exactly how much but it wasn't cheap.
Guys, if ones dyes in a washer, how does it work with cleaning it up afterwards? I always dyed out of the washer.
I wipe out the machine, trying to get into all those tricky hidden creases in the seals, and then do a wash-cycle with nothing in the machine, extra detergent and maybe a bit of bleach (as it's invariably black that I've been using)... it does say on the boxes not to use dye in a shared machine, clearly a cover-all statement on the part of the manufacturers.