Can an observer of women in red lipstick or more darker shades interpret anything related to their psychology?
Rarely does one find oneself wearing lipstick unintentionally, I'd venture to guess. Therefore, one can at least conclude simply, "They want their lips to look redder or darker." There is added information in this conclusion, however sparse, about the motives of such women.
You might then wonder, "Why would women want their lips to appear redder or darker?" You might also note that most lipsticks have this effect, or add gloss to lips that are often paler and more matte naturally. Therefore you could probably consider the function of lipstick in general, not only red and dark shades, because this already includes most. Here's a recent article you might want to check out...
Hill, S. E., Rodeheffer, C. D., Griskevicius, V., Durante, K., & White, A. E. (2012). Boosting beauty in an economic decline: mating, spending, and the lipstick effect. Journal of Personality and Social Psychology, 103(2), 275–291. Available online, URLs: http://gatorlog.com/handout/handouts/Hill_Rodeheffer_Lipstic_Effect.pdf, http://personal.tcu.edu/sehill/LipstickEffectMS20March2012.pdf. Retrieved January 7, 2014.
It mostly discusses beauty products in general, and uses lipstick as a particular operationalization of bueaty products, which might even be cause for some concern about their conclusions. In any case, it should give a decent introduction to how some psychologists think about the implications of lipstick in general. I agree with @KasperBruhn that you're unlikely to hear about any good empirical research about why women choose the colors they do, but you might...This question is already the fourth hit for a "lipstick shade psychology" Google search! Also, the first hit is pretty informative about the psychology of men viewing women with lipstick:
You've got to suspect that women know that they're doing this to us...The author clearly does! As for the Daily Mail's original contribution to the discussion:
Forgive me if I over analyze, but I assume that you refer to the fact that red lipstick in some places are commonly known to be a symbol of the woman trying to gain attraction.
In that case it doesn't say anything about her "psychology" rather her state of mind. But yet again everyone perceives these signals independently and it would therefore be a bit of a harsh conclusion to conclude anything from it.
According to the different shades of red, i don't think there's made any scientific conclusions that prove it has any connection to the woman's psychology. I believe it's a simple matter of what her taste is like.