[sp332]

I like most of these, especially the different ways of making a hierarchy stand out. But I would say that if you're going to use gray text, pick out the exact shade using a really crappy LCD screen, maybe on an old phone, to make sure it's legible. Sites that use very light gray make me think the designer picked the color on a 5k iMac with the lights off.

Also, make your buttons look like buttons.

[joshribakoff]

There's also automated WCAG tools that check for "contrast errors". For example you should ensure you provide background colors as a fallback if the user has background images disabled or the image has not downloaded yet