I'm not a big fan of changing HUD color for one reason only:
I don't quite like losing the red/foe and green/friendly color code which you inevitably mess with by changing the HUD color.
That said, I did change it a couple of times to match the rest of the dashboard on some ships:
The Orca's instruments glow yellow rather than orange, so I fly the Orca with these settings:
<MatrixRed> 1, 0.25, 0
<MatrixGreen> 0, 1, 0
<MatrixBlue> 0, 0, 1
For a result like so:
And recently on the Cobra MkIV:
<MatrixRed> 0.5, 0.5 ,0.5
<MatrixGreen> 0.5, 0.5, 0.5
<MatrixBlue> 0, 0.5, 1
For this result: