1. To change the color of land tiles you have to copy the tiles you want to use then change their color, then add them into the veradata.mul like any other add on graphic. Yes you will have two of the same items just different colors. Dont forget to create and change the color of the texture maps as well.
2. Draw the picture of any item you wish to have a transparent background on and either fill the background with true black (0,0,0) or use Mulbuilder (or simular) program and select the "Transparent" option under the "Draw Mode" panel.
3. That one you just check the scripts in POL or any other EMU that has the steeds and they will tell you the color. I would tell you but that would make it to easy.
Dev