Consider first the set Sm of all possible clock faces using m colours, where we consider two to be equal only if the colours match without any rotation: there are m12 elements in Sm. Let f be the map that rotates an element of Sm by 1/12 of a complete circle, i.e. 30 degrees. (f depends on m, but the action is the same regardless of m, so we just write f.) All elements x∈Sm have period 12 under f, but some have smaller periods. Let p(x) be the least period of x, and let nm(k) be the number of elements x∈Sm such that p(x)=k.
It is clear that the possible values of p(x) are the divisors of 12, and that the number of distinct clock faces, allowing at most m colours and counting rotated clock faces as being identical, is
N(m):=12nm(12)+6nm(6)+4nm(4)+3nm(3)+2nm(2)+1nm(1).
Since there are three ways to select two of the three colours, the answer to the problem is N(3)−3N(2)+3N(1); the last term is because each one-colour clock face is removed twice, so we must add it back.
To make the solution explicit, it remains to compute a formula for nm(k) for each divisor k of 12. It is clear that nm(1)=m.
Next, nm(2)=m2−m: we remove from the set of elements with period 2 those that also have period 1. Similarly, nm(3)=m3−m and nm(4)=m4−m2.
With a little more thought, we see that nm(6)=m6−m3−m2+m and nm(12)=m12−m6−m4+m2. For instance, for nm(12), we remove from Sm those elements with period 6 and those with period 4, leaving only elements with least period 12. However, when we removed the elements with smaller period, we double-counted those with least period dividing gcd(6,4)=2, so we add these back.
Explicitly, we obtain N(1)=1, N(2)=352, N(3)=44,368 and so the final answer is N(3)−3N(2)+3N(1)=43,315.