Just replace the Palette block in …/APC40/Configurations/GridPieEffectNavigatorTransportMixer.lua with the Palette block below:
palette = {
out_of_bounds = { color={0x00,0x00,0x00}, text="·", val=false },
content_selected = { color={0x00,0xFF,0x00}, text="·", val=true },
content_active = { color={0xFF,0x00,0x00}, text="·", val=false },
content_active_current = { color={0xFF,0x00,0x00}, text="·", val=false },
inactive_content = { color={0xFF,0x00,0x00}, text="·", val=false },
gridpie_current = { color={0xFF,0xFF,0xFF}, text="·", val=false }
},
This works for me!