• Understand the basics of color psychology and color theory. See here.
• Are your primary and secondary colors contrasting from each other?
• Do the colors of your primary actions (E.g. CTA buttons) stand out from the rest of the page?
• Do the colors complement the fonts and make them legible on all screens?
• Choose colors based on the emotions you want your prospects to feel when they visit your website/use your product. See here.
• See if the colors work well in responsive designs too.