There were only two colors left: red and magenta. Took magenta.
Magenta is closer to blue than red and is much better to distinguish from lightsalmon 
Not convinced it should not be yellow though...
The yellow system is already there (the magenta system was taken out of it when the roads transferred from department to metropole and they resigned).
Aah, I see it now -- frahdfd59, Nord Routes Départementales? I was quickly searching for "Lille".
On the one hand, I can see doing this. OTOH, there
appear to be no yellow & magenta routes within the same area; no yellow where there are also magenta, so do we really need to differentiate?
On the one hand, I see places like wghere
FRA-HDF M62-59,
FRA-HDF D62-59 &
FRA-HDF M145-59Hou all meet up, and the different colors provide some differentiation. OTOH, there will be department borders within regions all across France, and yellow routes meeting up at the borders, with no simple visual cues as to the different systems; so why have one that's different?
Similarly, should canmbw be a different color from canmbp?
They are Metropolitan Routes, signed in cyan (already taken as a colour), rather than Departmental Routes that are signed in yellow.
...
espct uses red signs, rather than the orange ones that other Spanish Autonomous Community systems have. There's also limited N Roads (also signed in red) in the Autonomous Community.
Meh, but are all the lightsalmon systems across Europe signed in lightsalmon though?
If system color went by signage, North American mapview would be an ugly mess; no uniformity. One would think that colors would be geared more towards showing systems' relative importance, and providing uniformity to map views.
