The LG Stylo 4 is a stylus-equipped midrange slate-format Android smartphone released by LG in 2018. Identifiable by model numbers L713DL and Q710(AL, CS, MS, TS, ULM, ULS, and US).
You may have turned on grayscale mode by accident. You can check your settings in your settings app, the grayscale option may be listed in the Accessibility settings under a category named "Visibility enhancements" or similar visual-related settings.
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Have you messed with any of the accessibility settings recently?
S. I. Dalton さんによる