fix: changes theme_color to gray 100

[grahamharper]

Closes #

{{short description}}

Changelog

New

• {{new thing}}

Changed

• changes theme_color to gray 100 / #161616. theme_color is used to tint the title bar in Safari 15 and Android Chrome

Before:

After:

Removed

• {{removed thing}}

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[vpicone]

Brilliant, looks great. Thank you!