Mixed spellings of colour/color used in mobile editor color picker

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Describe the bug In the mobile editor custom color picker, both "colour" and "color" are displayed on the same screen.

To Reproduce Steps to reproduce the behavior:

1. Create a post.
2. Invoke the custom color picker, such as creating a Cover block and setting a custom gradient color.
3. Note that the "Color" label and "Select a colour" prompt are both displayed on the same screen.

Expected behavior User should see appropriate spelling based on their locale, and different locales should not be mixed.

Screenshots

Smartphone (please complete the following information):

• Device: iPhone SE 2020
• OS: iOS 16.3.1

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After some initial investigation, this appears to be both device- and site-related. In the screenshot above, my device is set to en-AU Australian English (colour), but I believe my site is set to use the en-US American English locale (color). When testing in the default settings of the iOS Simulator, I noted that "color" was used in both instances (despite my mac OS laptop being configured to use Australian locale). While the spelling differences between colour and color are very small, it still suggests that it is somehow possible to mix two locales on the same screen, so there may be further combinations of more serious locale-mixing that is worth looking into.