1) Notice that there are three cats, and each collar has 5 options (colors).
2) Based on that, we can write the following, considering the repetitions of colors are allowed.
Thus, there are 125 possibilities (selections) for picking colors for this set of three collars.
Part 2) Given that now, it is not allowed repetitions we can use the same diagram with a little adjustment: the number of possibilities over the dash is going to be decreasing for each picking means one less option.
Since Dave cannot repeat any color, there are now 60 selections to be made.