I would like to change the color of some SVG pictures and then save them as PNG images. I have installed GIMP. I am running Ubuntu 14.04.
How can I do that?
You could install Inkscape, open your SVG file in it, do your edits, and use the File > Export PNG image...
option (Shift + Control + e) to do the conversion.
This is my standard procedure, and it works flawlessly. How well it works for you might depend in the source for your SVG, but certainly worth trying.
It should be possible to do this with Image Magick, as noted in another Q&A, but I always find that a bit trickier to control, and there's a bit of a learning curve there. It also appears that the "Converseen" front-end hasn't been updated for Ubuntu 14+, and its website has issues (so far as I can see).