I'd like to suggest that, rather than run a common [ black ] to every LED as a pair, that you run only a single common to each "geographical grouping" and daisy chain the commons there. For example, for 'Tower N' [ = 3 LED's ] you would have four wires instead of six: two greens, a red, and one black. This will result in less linear t/board requirements and, more importantly, will reduce the number of wires in the 'backplane' which will be of benefit in the more complex panels.
SZ
Edited to add: I also would like to suggest you use additional wire colors; for example, using the Tower N example, I wouldn't have two greens going to the same location. And if you have different commons, which may not literally be the case here though you seemed to have arranged them as such, I'd use a different color for the 'block' vs 'turnout' commons -- white perhaps. And how about a different color than green -- since you're using it for turnouts -- for the block +'s -- or better still, three [ at least ] colors.
