Is there any guidance or evidence about the use of contrasting colours for title vs body text of a webpage

Is there any guidance or evidence suggesting whether it is better* within the body of a webpage to have titles (and subtitles) in a contrasting colour to the body text? Does this improve readability of the page, or is it purely a design choice?

• by better, I mean easier for a user to scan / read a page and determine the key concepts described.