Edit: Link to original instructions: (reddit, E:D forums)

For those of you that have Photoshop, here's a quick'n'dirty way to preview your UI changes without having to load / reload the game. (Note, this was done in CS6, but I'm sure earlier versions can do it as well).

The imgur images are in an album. You should be able to get the gist, but just in case, here's some words to go along with the pictures.

Get a screenshot with all the UI elements you want / care about. Tutorial missions are great for this.

The example we'll be using: http://imgur.com/a/HceVj#0

Load this up into photoshop: http://imgur.com/a/HceVj#1

Add a Channel Mixer adjustment layer: http://imgur.com/a/HceVj#2

Now the fun part. For each channel (Red, Green, and Blue), you can set values from -200% to 200%. The values in the GraphicsConfiguration seem to range between -1 and 1 (that I've seen; I haven't tried to go beyond these values). So multiply by 100 and use those in the Channel mixer. We'll be using the following:

<Default>
    <LocalisationName>Standard</LocalisationName>
    <MatrixRed>     0, 0, 1 </MatrixRed>
    <MatrixGreen>   0, 1, 0 </MatrixGreen>
    <MatrixBlue>    1, 0, 0 </MatrixBlue>
</Default>

So, the Red channel will have 0% Red, 0% Green, and 100% Blue. Entering that... http://imgur.com/a/HceVj#4

Green doesn't change...

And the Blue channel will have 100% Red, 0% Green, and 0% Blue... http://imgur.com/a/HceVj#5

Our result in Photoshop: http://imgur.com/a/HceVj#6

And the result in game: http://imgur.com/a/HceVj#7

You can probably also do this in Gimp (free), but I'm not as familiar with that. If someone would post instructions there, I'd be happy to add them.

Enjoy!

Edit:

/u/OUberLord posted how to do this in GIMP below. Thanks!:

FYI you can do this in GIMP as well, like incizion mentioned. I don't like how I can't do a full screen preview of the results (maybe someone else knows how), but the Channel Mixer GIMP equivalent is found under Colors > Components > Channel Mixer.

You can drag out the preview window to some extent, but I wish it would just show the effects in the main workspace. Beyond that though, the rest of your instructions apply the same.