...
WAVE browser plugin
Lighthouse - built into Chrome browser
...
References
Links to extra support and other resources
WAVE Accessibility online site also offers a browser Extension, https://wave.webaim.org/
"Check Web Site’s (X)HTML & CSS, Accessibility & SEO," https://www.webnauts.net/check.html
“Color Blindness Simulator,” https://www.color-blindness.com/coblis-color-blindness-simulator/
a Firefox web developer addon, https://addons.mozilla.org/en-US/firefox/addon/web-developer/