Colored output looks bad on black-on-white terminals

[evmar]

TypeScript's --pretty output produces line numbers that show up as black-on-dark-gray when run on a terminal that is black-on-white. See the number on the left here. (Sorry for the giant picture, I run a hidpi screen.)

Suggested fix: if you set the background color in the output, also force the foreground color. I guess here you want to force white.

Also note that the special colors 38 and 48 are available for "the terminal's default foreground/background color":
https://en.wikipedia.org/wiki/ANSI_escape_code#Colors

[mhegazy]

PRs welcomed.