Not all interfaces have palette set. Which palette will be used?
Depends on the interface (and the source code).
Usually PAL_GEOSCAPE.
What is "id: palette" element?
It's an element for the background palette configuration.
Is it same as palette or something different?
Different.
What palette is used by UFOInfo interface?
PAL_GEOSCAPE
One example of my confusion.
The UFO detection popup. Apparently it uses two colors in the list but I cannot find any color setting code in the UfoDetectedState::UfoDetectedState.
Loading colors:
add(_lstInfo, "text", "UFOInfo");
Changing colors:
ss << Unicode::TOK_COLOR_FLIP << tr(heading);