Not everyone sees colours the same way and that’s why it’s important to understand how contrast affects your website.
What may look fine and completely readable to you, may be very difficult (or even impossible) for someone else to read.
You can check the contrast of different colours by using a tool such as the WebAIM Color Contrast Checker.
Use great colour combinations and help make your website as accessible as possible.
Colorzilla is a great tool for exacting colours from a web page.