If the frame is a solid main color, back tape seems to usually look best, especially when the saddle is black. Black tape, housing, and saddle to offset the bold color frame.
If a frame is black though, I like to sometimes match the housing to the accent color, and then tape matching the housing if possible. So black frame with red lettering would get red cable housing and red bar tape(cinelli on Amazon isn't expensive, good quality, and color).
A white frame can get away, in my opinion, with the same idea as a black frame- matching the housing and tape to the accent color.


I did up a navy blue Puch last fall with new decals- I picked orange since that contrasts well with the blue. After adding orange bar tape to match the lettering, I realized I had just built up a Chicago Bears themed bike!