Hello there!
You can change primary color on whole site following this steps:
1. Open customizer (Dashboard->Apperance->Customize)
2. In customizer Open Styling -> General
3. Change Primary color
4. Save changes.
https://prntscr.com/f3z9q7
If you want to change only the color of the site title ,
, the easiest way to do this is to make your website title as an image in a color of your choice ,with transparent background,(you can do it with a Inkscape ,free vector graphics editor.) and upload that image as logo.
customize->Header-> Logo
