To accomplish this, you will want to follow these steps:
In joomla navigate to Administrator → Extensions → Templates Manager and select the template you are currently using as your default.
Navigate to the Style tab.
- On Predefined Styles select the color you want.
If not satisfied with 4 ready styles on Custom Style select the color you prefer to have for your site.
Select for Text, Links, Background the colors you like to have in your site. You can let it also blank.
Select Background patterns you like to have in your site. You can let it also blank.
- Click Save button
Your site will get the style you select.