Someone should point out that under Beers-Lambert, most synthetic dyes have an extinction co-efficient of 10,000 or more. That indicates at 1 pt in 10,000 no light passes through a one-centimeter cell (at the indicated wavelength). That implies 100 ppm dye in solution gives you a black ink. For a pink Kool-Aid, use level is probably 20 ppm.
Dyes are very powerful and used at very low levels. Often they are sold highly diluted or extended with inerts. In the states, McCormicks sells food colors used for decorating cakes etc in small bottles. Iād like to know the per cent solids when sold. I suspect about 1%.
In Junior Achievement one company I advised made windshield washer antifreeze. We used methylene blue to make it light blue. You could not add crystals to the 10 gal tank. It was always too dark. Better to dissolve in a bottle and add measured amounts.
Dyes are very strong.