CSS is fun. And Adaptive Themes Core is a good place to do your own CSS customizations since it is so easy to subtheme it. and be aware, if you do want to do CSS stylings within the CSS files themselves in Drupal, you want to do it in a Subtheme. That way, the theme itself is still maintained by the original person and you can take advantage of the upgrades.This is a good resource for CSS styling and colors.
This is a good reference for colors and their hex labels. Hex is the best approach to color in CSS.
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