"You have red hair."
Translation:Tha falt ruadh ort.
Because for a Gaelic speaker what English calls red are two very distinct colours: dearg is for bright saturated reds of blood, red ink, paint, etc.; ruadh is the colour of red hair, animal fur, copper, rust (darker, less saturated brownish reds).
English might also use terms like ginger, copper, rust to refer to this colour but the default is still red – English red is a broader term that covers those colours too.
But in Gaelic one wouldn’t say dearg about something that is rusty-coppery-red ruadh – here those are separate colours.