Oh, I can believe that women can see more colours.
If they're tetrachromats, at least. If not, I wouldn't say so... *copies a citation from wikipedia: ^ a b c Jameson, K. A., Highnote, S. M., & Wasserman, L. M. (2001). "Richer color experience in observers with multiple photopigment opsin genes" (PDF). Psychonomic Bulletin and Review 8 (2): 244–261. PMID 11495112.
http://www.klab.caltech.edu/cns186/papers/Jameson01.pdf.*
They did a study in which they basically had people in a dark area look at something like a rainbow and mark lines between colors to delineate them.
1. Four-pigment females marked an average of 10 bands with a standard deviation of 2.96 and there were 23 of them.
2. Trichromat females marked an average of 7.6 bands with a standard deviation of 1.80 and there were 15 of them.
3. Trichromats (females and males) marked an average of 7.3 with a standard deviation of 1.93 and there were 37 of them.
4. Dichromat males (protanopes) marked an average of 5.3 with a standard deviation of 1.53 and there were 4 of them.
It says that the tetrachromats (group 1) were identified by "genotype analyses identifying heterozygote subjects." Also, the female trichromats (group 2) are a subpartition of group 3, and the results of the comparison between them and the male trichromats were: "Interestingly, male trichromats (n=22) and female trichromats (n=15) were not significantly different regarding the number of chromatic bands each group on average delineates (p= .44)."
They end with this:
"At present, four-photopigment female individuals are reported to be rather common, by some estimates occuring in up to 50% of the female population (M. Neitz, Kraft, & J. Neitz, 1998). It is also the case that an estimated 8% of males presumed to be color "normal" likely represent a four-photopigment retinal phenotype (expressing multiple L-pigment opsin gene variants that could significantly contribute to color vision; Sjoberg, M. Neitz, Balding & J. Neitz, 1998). All else being equal, our results suggest that if such males were tested in the present study, they would perhaps exhibit an extended percept relative to "normal" trichromats, similar to our findings for heterozygote females."
In other words, it sounds to me like they THINK they should have been able to detect any tetrachromat males that were in their study, and since they didn't, they probably think that they just happened to not have any in the study (it only had 64 people in it; 8% of 64 is 5.12 but with random chance being what it is there's still a chance of getting none).