I've been collecting links to various resources. Hopefully, these will be of use to you.
WebAIM's Contract Checker is a nice tool to check if the contrast between the background and the body text is enough for each WCAG level.
WebAIM's Link Contrast Checker lets you compare background, body text color, and link color for the cases you are using only the color to identify links.
Who Can Use - A great tool that brings more attention and understanding to how color contrast can affect different people with visual impairments. It lets you compare the background and foreground with text color and boldness.
Accessible Brand Colors shows you how ADA compliant your colors are in relation to each other. You can add all your brand colors to this tool and see what combinations of them you can use.
Sara Soueidan's blog post A guide to designing accessible, WCAG-compliant focus indicators. This post also refers to the WCAG 2.2, which is not yet released at the point of writing, so check those examples out and make sure you are already compliant with the new rules as well.