When should bold, italics, and colour be used to draw attention in a sentence?

Following is my signature on some other fora:

Interested in Drawing, Painting, and Crafts?
Please Commit to the Arts and Crafts Stackoverflow proposal!

I cannot show it here but the words "Drawing, Painting, and Crafts" besides being bold and italics, also have font colour green.

How to decide when to use bold, italics, and colour to draw attention in a sentence?