
Initially, I've tried to issue first K1 unicolor guesses to determine counts, but it turns out it wasn't necessary. This approach gets no information about ordering from the first guesses, and I've got ~100 score from it (my second submission). I did not participate in this match, but I thought of the first phase of finding the counts of colors: First try k1 guesses with 2 colors in each guess (half of one color, half of other, randomy sorted).
let`s call the numbers of pegs in each color A,B,C,D. Then (for 6 pegs) You have: guess: ababba, result:1 miss,1 hit, equation: C+D=62 guess: ccacaa, result:1 miss,0 hit, equation: B+D=61 etc.. and last equation: A+B+C+D=6
Assuming that no peg color constitutes more than a half of the key, this will give the number of pegs and some information about placement in k guesses. But I guess the further part of telling which peg goes where was the difficult one :) 