OK well first you dont need it in color black and white will be fine also without matieral faces will be fine. Make sure no pieces are over the edges of your paper and make sure you have paper sizes correct. ALso if you have the defaults the solid lines are cut lines and the - -- - -- - are usually valley lines and the - - - - - are usually mountains check in the line settings. Also print one page and check to make sure it all shows up properly when printing so you dont waste paper. Also watch it print and check each piece to make sure it doesnt screw anything up. Also if you do screw up just flip the page over and print on the other side it really wont make a difference.
I elected not to, just because it would just take up more of my printer ribbon. The colors are fairly light, so it shouldn't interfere. Under the page setup, if you made your lines less transparents that will help too. If you think the color will help act as a guide, and will help you out, then go for it. (and if your parents aren't gonna kill you for blowing the color ribbon )
I'm goint to print the lines in diferent colors so I won't screw it up and turn a mountian fold into a valley fold but that's the only color I'll be using since I don't want to eat up my ink supply, which is a only half full so I won't be getting a full suit printed out before the tanks run out.
Folds and valleys really don't matter too much - choose which line style is which, and then go for it that way. If you do it one way rather than the other, you'll just end up with all the numbers on the inside.
Also, there's no need for color. Match up the numbers, and glue. It's simple - me and my brother have been putting a Scout helm together for the past three days without a problem.
Having played around with graphics for a few years I know what goes into making a chosen color so if you use a primary or secondary color you can get things printed without using up a lot of ink, becides this is just printing lines, not solid areas which is what really uses up the ink.