I have this problem with blues too .. I just can't focus on them well. It even works for me with blue (0,0,255) font color on black background. It's pretty hard to read.
IMHO it's because rods or not sensitive to blue .. so you see blues only with cone cells. And those are pretty sparse, especially the blue ones.
I remember once I worked with spectrograph in school lab .. and we measured sunlight spectrum. You could look inside to see any wavelength you set it too .. and on the 'fast side' of the rainbow, I could not see purple as far as I could go. Pretty strange color, but definitely blue. I totally did not understand why they say 'ultraviolet' .. when it's ultrablue in my eyes !
But it seem to differ for some people.