If you're looking to use a consistent color, whether in a button or text throughout the site as a Brand Color, and you're looking to match the exact shade or hue, you can copy-paste the HEX code. Every color has its own unique HEX code and is visible when selecting a color.
For example, here's how to use a button color HEX code that's copy-pasted from a different button on the site...
1. Hover over the existing post where the button color you want to use is displayed, and click on the "edit" option.
2. Click the Button Color swatch to reveal the HEX code inside the color editor.
3. Copy that code and paste it wherever else you would like to use it on your site.