My daughter has some strange habits. Like completely washing her shoes including soles before and after every wear and wetting say black jeans to make them more black because every shade of a colour that she wears has to match perfectly. I have been happy to let her get on with it up to a point but now she is drenching everything under the tap before putting it on. Shoes and all. I cannot let her go out like this and my husband is outraged I have let it get to this point. She will meltdown if I interfere with anything she does and she is becomes agitated at any demand I make of her. I am absolutely lost on how to cope with this and help her with this compulsion.
I can understand your daughters obsessions with colours and tones. If she is insistent on everything being very black in colour and tone, then I have achieved this in the past by buying clothes that are white or grey and consist of similar textile components, only to dye them one colour, such as black. I found that in most cases, the results were fairly satisfying although not perfect. I'm not saying it will solve the issue, but might be an option to explore. Maybe if she is involved in the process she will be more connected and accepting of the results.
I used to colour my textile trainers in black marker pen as well, which I would touch up regularly for an even coverage and tone.