The number of all possible outcomes is 6*6*6 = = 216 in this situation.
There are 6 possible outcomes for each colored fair die, independently.
Solved and explained.
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You may ask me, what is the role of coloring ?
It makes all 216 outcomes distinguishable.
Had the three dice be undistinguishable (identical), then some (~ many) of 216 outcomes would be undistinguishable;
so then the total number of distinguishable outcomes would be less than 216.