Heres what I did for this:
http://nldc.interfix.net/i11283
Steps:
Enter Paint.
Open 4 seat hyper cartexture.
Go to the no limits editor.
Get the red, blue, and green values of your train.
In paint, create a custom color.
Enter the red, blue, and green values.
Using the bucket and brush, color the section above the wheel that color.
Find a cool font.
Use the Abc tool with a see through backround.
Draw a box that fits in the right place of the train(About mid section)
Type in what you want on the train.
Size it so it fits the way you want.
Save cartexture as your ride name into the cartextures file as a PNG file.
Go into the editor.
Hit coaster setting.
Find trains.
For each train hit apply cartexture or whatever.
Find yours, and apply.
Your done!
For different colored trains, make multiple colors with all the steps above. I hope this works.