From an engineers perspective, whenever specifying colors from now on we should use the form:
```
color: rgb(var(--tone-red-500));
```
Please note:
- Use rgb. This lets us do this like rgb(var(--tone-red-500) / 10%) so we can use a 10% opacity red-500 if we ever need to whilst still making use of our color tokens.
- Use --tone-colorName-000 (so the prefix tone). Previously we could use a mix of --gray-500: $gray-500 (note the left hand CSS prop and right hand SASS var) for the things we need to theme currently. As we no longer use SASS we can't do --gray-500: --gray-500, so we now do --tone-gray-500: --gray-500.
Just for clarity after that, whenever specifying a color anywhere, use rgb and --tone. There is only one reason where you might not use tone, and that is if you never want a color to be affected by a theme (for example a background shadow probably always should use --black)
There are a 2 or 3 left for the code editor, plus our custom-query values
John Cowen