Radio channel improvements

[NikkoJT]

Identified some issues with radio channels:

• INDFOR channel colour is not sufficiently distinct from group
• Channel checking is not always reliable
• LR can be difficult to identify when colourblind

[SamLex]

Testing on dev (06ff60f) - PASS

• In non-dedicated MP with a mission created directly from the template:
  • Confirmed INDFOR colour is different from group colour
  • Confirmed LR channels have identifier character next to them and get callsign in text
  • Confirmed slotted Zeus gets access to all channels, both in split mode and non-split mode

Can't really check the reliability improvements, but field testing has probably been sufficient for this.