Can I change the colours of the titles in Drupal?

You are creating a page and when you have a look at it, you find a little bit boring. Then you think, if I change the colour of the titles, it would become nicer.

You have the possibility to modify the size of the titles in order to create a structure in the content you put on the page, but you can't change the colour, why?

1. The visitors on our websites don't come in order to evaluate the design of the page you have created, they come in order to carry-out a task or to find information in order to get "job to be done".
2. Too much colours on a page, makes it very tiring to scan and to read.
3. We want to keep some concistency through the website and between our different websites so the visitor knows and gets the feeling, I'm on a SD Worx website.