1 - I think that the color of the 3D HUD is controlled within the gauge file (CSWeapon.dll), so I don't think you can modify it. :(

2 - I think the only way you could resize the 2D HUD for the exterior view would be to make a 2nd 2D HUD window in the panel.cfg. Like this:

[Window Titles]
Window00=Weapon Control Panel
Window01=HUD
Window02=HUD Glass
Window03=GPS
Window04=Exterior HUD

[Window04]
Background_color=0,0,0
no_luminous=1
size_mm=400, 400 <- Reduce the size from 400, 400 to something smaller
position=4
child_3d=0
visible=0
window_size=0.380, 0.600
ident=10902 <- This one can't be the same as the one in [Window01] or it causes problems. I'm not sure if it will work if you change it though
zorder=1 <- This needs to be changed too. I think.
gauge00=CSWeapon!hud2d, 0, 0, 400, 400 <- Make sure that the last two sets of numbers mach the size_mm= entry

If you don't use the 2D HUD when in the VC, then just change the [Window01] to suit yourself for when in an exterior view. ;)