Thanks for that Alex.
The process I followed was:
1. Downloaded icons from https://github.com/albar965/littlenavmap/tree/release/1.4/resources/icons
2 Copied them to the C:\Users\whitehaven\AppData\Roaming\ABarthel
3. Edited the files in Inkscape, filled icons with colour and then saved.
4. Loaded Little Navmap, no change.
I will try again, ATB Dave