Problems with Display Colours

I am new to I-macs but have been using Windows foe many-years.
I recently clicked a tic box which put me into the grey scale mode.
Now I do not know how to restore Colour mode.:
Frank K

I changed the title of your thread - your name doesn't tell us much about your problem.

Go to System Preferences > Universal Access > Seeing > uncheck "Use Grayscale"