Consider using a different color palette under dark mode

[han190]

The Fortran logo and most of the accent color uses #553276, which is fine with the white background. But under dark mode, the purple color used (#553276) and the background (#121212) does not create a good contrast (see contrast checker). Maybe consider using the color palette from One Dark Pro?

[henilp105]

@awvwgk @fortran-lang @han190 Please suggest colour theme/pallette for dark theme.

Thanks and Regards, Henil Shalin Panchal

[henilp105]

@han190 Please feel free to recommend palette for dark theme.

Thanks and Regards, Henil Shalin Panchal

[ShrutiPriya13]

I think #C0ACD2 this colour would be great in dark theme too