Hi, sorry for the late reply, I hope you get this message.
First thing to say is that I’m not a DNA analyst so this isn’t my area of expertise. I also don’t look for DNA in my samples, I characterise them based on their chemical profiles and visual appearance.
What I can say is that I’ve found that the darker shades of makeup I’ve analysed seem to be more heterogeneous (meaning less well mixed) than their paler counterparts and I’m currently investigating why that might be. My guess is it’s due to the increased pigment content, relative to the matrix it’s suspended in. The main pigments used in face makeup are oxides of iron – yellow, red, and black – and these are mineral particles. So the increased number of pigment particles is likely making the darker shades more heterogeneous.
With regards to finding DNA in makeup, I can’t imagine that it would be any different to finding DNA in pale makeup. The standard method of DNA collection is swabbing so whether you swab a light sample or a dark sample, shouldn’t make any difference 😊