When writting the html tags..how do they get their colours

Answer 1

... with CSS.
Html alone is quite limited.
Css is unavoidable if you learn Html.
And maybe you will learn at least a few of javascript, to be able of handling you Html/Css more dynamically ;)
in reality, inherited from previous versions, you could found some attribute allowing sťyling working (such as color, background color...), but are deprecated and/or obsolete, and shouldn't be used nor shouldn't be known ^^

Answer 2

use attributes with elements or betterbyet CSS