There are two sets of these red marks, one on top, the other on the bottom. This lets you see one set of marks whether the bike is right side up or upside down. I have a very nice 1970's Peugeot racing frame which I have converted into a Nexus 7-speed. Frames for use with the Nexus system must have horizontal drop outs . Bikes with vertical drop outs don't provide any way to adjust the chain tension, and they cause problems with cable routing.
Older bicycles are typically narrower than that.
Any good bicycle mechanic will be able to do this. In the case of aluminum or carbon fibre frames, the spacing can not be adjusted, but few frames of these materials have the necessary horizontal drop outs anyway. The other is the issue of axle rotation. Internal gear hubs try to rotate the axle in the frame in certain gears. It tries to turn one way in high gears, the other way in low gears.