To create a custom style using the colors from your website, you'll need a program that can tell you the hex code of those colors. Then you'll use those hex codes to change the colors in your own, custom style. Whether you're a Mac, or PC user, there are free options, and also software you can buy for added security and functionality.
There is a built-in feature you can use, called the Digital Color Meter.
Color Picker Suggestions:
Instructions for Anny Studio's Just Color Picker: