Canon Canonet G-III17 Manual page 8

Pre-Settings
Wind the film advance lever until it stops.
The first frame is now automatically in
position.
7
Checking Correct Film Loading
The film is properly loaded and advanced
if the film transport indicator flickers when
you wind the film advance lever.
Checking Proper Winding Film
The film is wound up if the color of the
film indicator turns red. The indicator turns
white when the shutter is released.