A signal has $6$ flags, each flag can be blue, white or red. Possible signals formed is $n^r = 3^6 = 729$ possible signals formed
How many different signal can be made from $6$ flags of which $3$ are white, $2$ are red and $1$ is blue?
Order does matter - so permutation is this a case of $3! \cdot 2! \cdot 1!$ so $6 \cdot 2 \cdot 1 = 12$ ways? I'm not sure if this is right ...
The number of choices for the blue flag is $6$. For each of these choices, there are $$\binom{5}{2}$$ ways to choose the two red flags of the remaining five flags. The last three flags have to be white.
This gives a final answer of $$6 \cdot \binom{5}{2} = 6 \cdot \frac{5\cdot 4}{2} = \boxed{60}$$