In reply to j99:
How much climbing/scrambling/walking experience does your friend have?
My personal feeling is that 1's are easy (hardly need protection)
Grade 2's are easy climbing but usually have unprotected (often exposed, loose scree) walking sections between the cables, which I find makes them mentally tiring.
Grade 3's are my limit of climbing ability. Mostly fun with the occasional scary bit, usually enough sustained rock though that you are on a near continuous wire.
Col Rodela (grade 3) is a good intro if your friend has climbing/scrambling experience, it's a very short route with no exposure on the approach and descent. Minimal walk in, lots of exposure on the cabled sections with good protection.