No idea about that game (saw the thread in the "newest" sectionover in Elite Dangerous). For one thing, you might play around with the gamma values - of your display, your OS and even the game (if it has a corresponding setting).
If that doesn't help, you could give The GIMP a go. Gimp is an open source (free as in both free beer and free speech) pixel graphics program that is designed to be an alternative to Photoshop. For some things, PS is better - and especially some of the commercial PS plugins are better - but for your everyday image manipulation needs, it's more than sufficient. The official source is
https://www.gimp.org/ . If you want (scroll down on the "Downloads" page), you can also download the source code, change it and build it yourself (FOSS)

.