I have nine 3/4 runners, almost full-grown ducklings hatched this year. Mum was a call duck x fawn and white runner and dad was a purebred fawn and white runner. No idea on sexes yet, six are fawn and white and three are darker brown and white.
Comparing them with my pure-breds, I'm not sure you would have known they were 3/4 if I hadn't said.
I'll try to get a photo, when they come down from the ghyll at some point today.