I want to stripe the color in the decorating bag and I have never done it before. I was wondering if anyone can tell me how much coloring to stripe the bag with. And also, does it matter where i put the color in the bag? Thank you very much.

This page from Wilton may help you.
http://www.wilton.com/decorating/icing/coloring-icing.cfm

Also, do some experimenting on your own to see what works for you.

I played around with this method and tipped some roses. I painted the color on the crease of my plastic disposable bags. I did not use my feather weight ones, because I didn't want to dye my bag. Do not use a lot. Sorry about the graininess of the pic.

I personally found it easier to do the striping in a parchment bag not the plastic disposables. The plastic bags to me, repelled the color, where the parchment bags I could control the stripe better.

I tried the striping the last cuppies I made, but no pics. I put a really solid line of color in pink and purple with a small paintbrush in 4 equally spaced stripes. Maybe 1/4 inch wide for 18 total cuppies. What happened for me is that the first maybe third were way too dark. The pink was actually red and the purple was more blackish navy looking. (I know, I got red when I didn't try and can't get red if I try!) Then the color quickly faded and the last third had hardly any color. Very uneven technique. I preferred ones I made using different colors of bc in the same bag. If you do the striping don't over apply the color and plan on starting a new bag when the color fades. But it was fun to try, give it a shot and play with it.