cheapie suggested using signs_lib as a soft-depend (add signs_lib? with the question mark to whichever of your sub-mods' depends.txt is appropriate) and using it to provide traffic/street signs on your traffic lights' posts. In response, kaeza used his usual kickass skillz and added full multicolor text support to signs_lib, so that we don't have to keep hard-coded fonts in different colors.
kaeza says signs_lib will copy the node def when it creates the sign-on-post version of the node, so it shouldn't interfere with digilines compatibility. I believe all you have to do is supply a suitable nodebox model basically showing a sign on the post. I'm not entirely sure, as he wrote this code. :-)
I'd suggest making the actual sign's texture green with white edges and recommend to users of your mod that they write the text in white, at least that's how such signage is done here anyway. I guess in your locale, webd, it's black on yellow, so maybe offer both color schemes. ;-)
With the current version of signs_lib, as folks surely will see in
the homedecor thread, one would get white text by writing the white color code, #f, immediately in front of the text on the sign, e.g. "#f Exit 1, Minetest Heights ---> " or similar.