I hope you know the basics and know that if you want to change the colors, that you need to modify CSS file. If you are using Default Clean theme you need to do following steps:
Open the FTP server where you have your nopCommerce site, go to Themes -> Default Clean -> Content -> css, and open the styles.css file.
Go to line 1773 and find the .overview .product-name h1 selectors.
In default theme you will have only specified font-size and font-weight for that element. What you need to do? Just add the new property - color.