Internet browser question- change color schemes?

Is it possible to alter an internet browser's settings to alter the color schemes of a website?

I've been coming across this problem lately where websites will have a white background and then gray or very lightly colored text making it incredibly hard to read without moving my face very close to the screen.

Can you change the color schemes, or is that always going to be dictated by the individual sites you are visiting?

(and before someone says "get your eyes checked," I had an optometrist visit last year and have had 20/10 vision for years)