The radars are currently very un-customizable. This is problematic to people who are colorblind, and it is just limiting in general even for those of us who are not.

I propose that all colors used by the radar be made editable, just like the chat colors and such already are.

Secondly, it would be nice if we could assign different shapes to the types of dots as well, e.g. hostiles are triangles, friendlies are circles, and duelists are squares, or whatever we want. Shapes would include circles, triangles, squares, stars, diamonds, upside-down triangles, and maybe upside-down stars (anything much fancier would probably be hard to distinguish).

Thirdly, it would be very nice if there was a lua API to override the radar's selection of shape/size/color/transparency (and any other parameters you add), on a per-ship basis (rather than globally as above). I would very much like to make a plugin that lets me flag specific people to show up with one color/shape, and other people with other colors/shapes, etc. We could then make plugins that let a group-leader flag priority targets, important people to defend, and so on. It would also be very handy for fights involving more than two teams.

Currently, the closest we can come to doing those sorts of things is by overriding the hostility detection to control whether people show up as red or green, but that is very limited and can interfere with other systems (target-nearest-hostile and auto-fire come to mind).

+1. Even just having the colors configurable would help color blind people a lot. There could be maybe some color setting suggestions or profiles that work well with different types of color blindness.

+1

You'd figure things like text color, radar colors, etc would be part of the skinning feature...

Kabumpski

This would be of help to me. As I am colorblind myself.

From raybondo, February 13, 2015

iup.radar appearance properties
BLIPCOLOR%d
BLIPSIZE%d
BLIPTEXTURE%d

%d is a number from 0 - 23, with each number representing a specific blip type
7 = duel mode
8 = group member
10 = powerup
11 = stations
12 = storm exit points
13 = regular exit points
21 = wormhole

Friendliness
4 = good
23 = mostly good
22 = mostly bad*
5 = bad*

Some aren't used anymore or are unassigned

*original message: 4,23,22,5 are good, mostly good, bad, most bad friendlyness values

Found some more codes:
0 = target selection circle (red)
2 = own missiles/mines (blue)
6 = other player missiles/mines (yellow)
9 = roids / station objects (white)

14-20 seem to be invalid (cause the client to crash if I try to change the blipcolor)

Oh hell yes. For those wondering how to actually use this, you have to add the properties to the radar objects, which are currently at HUD.radarlayer[2][1][2] (front) and HUD.radarlayer[2][3][2] (rear).

Found one more color:
3 = blink color for homing weapons (red)

I get the same crashing with 14-20 that meridian mentions. So, that just leaves id 1 unaccounted for. I've got it set to a yellow-green color that I should notice easily if I do encounter anything using it.

I don't know under which conditions the game actually uses the mostly-good/bad in practice, but the mapping to GetFriendlyStatus works like this:
0 = bad, radar blip 5
2 = mostly bad, radar blip 22
1 = mostly good, radar blip 23
3 = good, radar blip 4

So, for the purpose of the target-flagging I was wanting in the OP, we now have potentially four categories to choose from instead of two.