SVG to STL conversion to make symbols recognisable for visually impaired users
If you install inkscape, pstoedit and ghostscript version 9.21 (not the latest as pstoedit is incompatible)   you can get the file into a format that openscad can 
import using two commands in a cmd file 

"C:\Program Files\Inkscape\inkscape" -E "traffic lights.eps" "traffic lights.svg"
"C:\Program Files\pstoedit\pstoedit" -dt -f dxf:-polyaslines "traffic lights.eps" "traffic lights.dxf"


then in openscad

linear_extrude(3) import ("traffic lights.dxf");


will import gives me 



With a thickness of 3mm - you can see the model needs some scaling but its seems possible although - I can't see an option to scale based on color -