LoneColor is a free portable 42KB program with a single, simple function: setting your Windows/ Android wallpaper to a defined solid colour.

Run the program on its own and your background will be set to a random colour. Add LoneColor to your startup folder and it'll change every time you boot.

On the PC, if you have a general colour in mind, just rename LoneColor to specify it ("LoneColor.exe" > "LoneColor Red.exe", say, or "LoneColor Cyan.exe"). The program then sets your background to that colour every time it's run.

For extra precision, it's even possible to specify the precise shade via its six character hex code ("LoneColor #7700AD").

On Android, copy a colour code from anywhere and tap the icon to use that shade.