One way to colour your soap is to use natural colours.
There is a large range of plant powders you can use to colour your soap, most of them will give your soap muted, earthy tints. I find they work great in natural soap as they emphasize the natural provenance of all ingredients used in your soap.
What natural colours can you use?
Turmeric for yellow to orange (depends how much you use. For a light yellow let the turmeric seep in olive oil and use the liquid only. Or for an intense colour add the turmeric powder directly to the soap);
Paprika powder for orange (please make sure it’s not smoked paprika or even worse hot paprika!);
Cacao for brown (the pure powder with no additives, not cocoa which contains sugar and other additives);
Activated charcoal for black;
Indigo plant powder for blue;
Naturally coloured clays (pink, light orange, green, brown);
Alkanet for blue, but sometimes it turns grey;
Madder root for peach colour;
Orange peel for orange;
Green tea powder for yellow-green;
Moringa leaf or spirulina for green.
Please see below a video of mixing your soap batter with activated charcoal.