arbitrary value for color needs hint but should arguably be detectable without it.

[crswll]

What version of Tailwind CSS are you using?

For example: v3.0.23

What build tool (or framework if it abstracts the build tool) are you using?

For example: Play

What version of Node.js are you using?

For example: N/A

What browser are you using?

For example: Chrome

What operating system are you using?

For example: macOS

Reproduction URL

https://play.tailwindcss.com/Flb7YuMeyy

Describe your issue

You need to do bg-[color:hsl(var(--h),50%,50%)] when bg-[hsl(var(--h),50%,50%)] should arguably suffice.