ds8 went to kindergarten not knowing the names of all the letters, he was taught the sound that each makes in the montessori school and hadn't yet learned the names for them all yet. and of course he was terrible at learning his colors, and i later realized that was because he was colorblind, poor kid.
don't worry about it at all, really. ds8 is highly intelligent, does very well in math and reading.
ds4 still doesn't know his colors very well ... again, we strongly suspect it's due to colorblindess since his wrong guesses follow the same pattern as ds8's, confusing green and brown, confusing pink, blue and purple all as blue.
he can count well to 40, i think, but misses a number or two, i think 14 is one for some reason.
but he doesn't map the number in his head well with the written number yet.
the preschool teacher explained it to me that a lot of stuff is developmental, and trying to teach a child something they just aren't developmentally ready for yet is an exercise in frustration for YOU. all of a sudden when they are developmentally able, it will just click for them and they'll learn it quickly. so don't stress out about it. she's a bright girl, she'll get it.