Create a board with 2 3-bit registers (in the Blue and Red halves) and two terminators.
If the numbers if the registers are equal, intercept a ball (either color) in terminator A.
Otherwise, intercept a ball of the color of the lesser register in terminator B.
IOW, if the left-hand register is less than the right-hand register, intercept a blue ball in terminator B.
I solved this with a very large virtual board. My solution is wasteful and can be made smaller, but I don’t think this is solvable in the stock board (except maybe with 2-bit registers).
Solution (left terminator means equal; right terminator means unequal).
Much-harder challenge (I didn’t even try): Intercept a ball of the color of the greater register.