GIMP

https://www.youtube.com/watch?v=YG-GxZhhJdI

https://www.youtube.com/watch?v=aiy2m-ic7ME

https://www.youtube.com/playlist?list=PLM6xCLAr1t5pZNZYqEfT3jiJehao3qnrS

if you want to find invalid color in gimp, tools > selection tools > by color, disable antialiasing/feather and set threshold to zero in tool options, hold shift, and click all of the 5 colors somewhere in the image to select them, then invert selection (select > invert). selected pixels will be the bad ones

Tips for labeling for noobs from a noob using GIMP (started using GIMP about 12 hours ago). Most of this is covered in the comma10k README

1. Don't worry about the "masks" files, you will be working with the "imgs" files. When you upload them you'll be uploading to "masks"
2. Use the free select tool and make sure "Antialiasing" and "Feather edges" option is unchecked
3. The color slection is super easy, just use the code provided at the github README
4. Create a new layer for each labeling catagory
5. Start with "undrivable" and highlight all. Then do the road. Then movable, then lines, then my car. I've found this order helps make sure everything gets covered.
6. Export as .png file
7. Take some time to understand what github is, and how it works (again I've only started using this <12 hours ago, so I have a ton to learn but try to learn the basics quickly.)