[system] Passing incompatible `grey` color to palette does not throw

This issue exists in alpha.36

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

When creating a custom Chip variant+color combination, I see an error in the JavaScript console that throws an exception. Note that custom variant props work, but not color.

Expected Behavior 🤔

I should be able to customize both the variant and colour of a Chip.

Steps to Reproduce 🕹

https://codesandbox.io/s/mui-chip-error-1vntn?file=/src/index.js

Steps:

Context 🔦

I started receiving this error message after upgrading from alpha.24 to alpha.36

Your Environment 🌎

`npx @material-ui/envinfo`

  Don't forget to mention which browser you used.
  Output from `npx @material-ui/envinfo` goes here.

[alexplumb]

Fascinating - thanks so much! This change actually makes the original code sandbox work as well. So strange - should the issue title be changed then? I’ll leave that to you folks 😃

[eps1lon]

Agree, the typings are correct, but for this specific color I believe we can add runtime check as well +1

Ideally the shape would be consistent to begin with considering the Color interface (the one with the A100 etc swatches) is something specific to Material design as far as I can tell.