When you read a comma in writing, there is a pause in the flow of the sentence, like there would be in speech. Overusing commas can distract from the point you are trying to make.
I find the Oxford comma is completely unnecessary. If you find yourself in a situation where you feel a common turn of phrase (like black and blue) necessitates the addition of a comma, try switching around the items in the list (i.e. 'black, red and blue' vs. 'red, black and blue'). Less commas == more flow.
PS. I am only posting my 2 cents because you misused "it's" in your last parenthetical.
I find the Oxford comma is completely unnecessary. If you find yourself in a situation where you feel a common turn of phrase (like black and blue) necessitates the addition of a comma, try switching around the items in the list (i.e. 'black, red and blue' vs. 'red, black and blue'). Less commas == more flow.
PS. I am only posting my 2 cents because you misused "it's" in your last parenthetical.