Update color-modes.js (#38626)

Update color-modes.js (#38626)

* Update color-modes.js

Fix IF statement in the prefer-color-scheme change listener always evaluating to `true` and changing the theme to "dark" even when "light" is set as the preferred theme.

| `||` | `x !== "light"` | `x !== "dark"` | Result |
|--|:--:|:--:|:--:|
| `x = "light"` | ○ | ● | ● |
| `x = "dark"` | ● | ○ | ● |
| `x = "auto"` | ● | ● | ● |
| `x = "bogus"` | ● | ● | ● |
<hr>

| `&&` | `x !== "light"` | `x !== "dark"` | Result |
|--|:--:|:--:|:--:|
| `x = "light"` | ○ | ● | ○ |
| `x = "dark"` | ● | ○ | ○ |
| `x = "auto"` | ● | ● | ● |
| `x = "bogus"` | ● | ● | ● |

* Implement re-read of stored theme