Created attachment 171683 [details] Screenshot with LibreOffice Dark color scheme Via Tools > Options > LibreOffice > Application Colors: AutoSpellcheck (under Text Document) it is possible to change the appearance of red-lines (wavy lines that indicate spelling errors). Changing the color has no effect until the paragraph is checked again (eg after changes to the text or return at the end). In the screenshot the Arabic text was checked with Dark Red font color. After changing it to yellow the wrong language under Hidden Text was added.
I confirm it with Version: 7.2.0.0.alpha0+ (x64) / LibreOffice Community Build ID: 1675a68526c43c6c6e4dc850ee911f0c1de75c88 CPU threads: 4; OS: Windows 10.0 Build 19042; UI render: Skia/Raster; VCL: win Locale: de-DE (de_DE); UI: en-GB Calc: CL
Repro Version: 7.6.0.0.alpha1+ (X86_64) / LibreOffice Community Build ID: f4c24da1e7f11664e0d2f688d2531f068e4a3bc0 CPU threads: 4; OS: Windows 10.0 Build 19045; UI render: Skia/Raster; VCL: win Locale: fr-FR (fr_FR); UI: fr-FR Calc: CL threaded