Thx, CM.
As regards the Doctor, it is pretty difficult to decide whether his unifrom is green or blue ... it's actually something in between. Luckily, in GIMP there is a scale to choose from - so there are like hundreds of shades of blue and green and lots of "in-betweens" to pick the one you like from. So I played around with the colours a little and it resulted in the above wallpaper.
Also, the end result, i.e my wallpaper, depends on many other factors as well. Like how well the room the scene was shot in was lit (on VOY, usually very badly unfortunately

), how close or distant the actor was standing to the camera when the scene was shot and - most importantly - what quality the original screenshot is. This means that the quality of the wallpaper greatly depends on whether the original screencap comes from a VHS version or a Blu-ray version or whether it comes from an original copy or a pirate copy, etc.
I normally use this website for the original screenshots:
http://voy.trekcore.com/gallery/index.php
However, the quality there is hit or miss (but I haven't found a better website yet). Like I have recently started making wallpapers for DISTANT ORIGIN and the quality of the original screenshots is ... poor - to say the least.
I only have the show recorded from the television and so it's not very good quality I'm afraid. Add to this the fact that my PC disables the printscreen function most of the time although in about 20% of the cases it works. The quirks of Microsoft Windows, I suppose ...
On a related note, someone I know told me once that she had been to a convention where you could see the actual uniforms that were used for VOY. She said the Doctor's was totally blue in real life. Which came as a shock to me because on screen it comes across as green rather than blue.