converting similar colors into single color

greetings everyone! i have a design that i want printed on a tshirt. the design has about 5 different colors....blue, green, orange, etc. when i enlarged the image, photoshop added in all these other color blue-ish, green-ish, orange-ish colors to make it look more genuine. but i just want the blues to be one shade of blue and the greens to be one shade of green etc! i figure this should be something photoshop can do, i just don't know how! can anyone help? thank you!!!!!!!

Well if you apply a pallette (a limitation to the number of colors and types of color) you will achieve this goal, but it wont look as nice as I am sure you would like it to. I am slightly confused by what you mean by "enlarged the image" and how that would add colors, but I think I get it what you mean.

For the "best" result you should consider doing it manually with the Pen Tool. Especially since it is only 5 colors you could whip it up in about 30 mins to an hour depending on how many pockets of color there are. If you need help understanding how to use the Pen Tool there are many tutorials, here is one:
http://www.melissaclifton.com/tutorial-pentool.html

If you post the image we could get a better understanding, maybe try some techniques ourselves, and, if you wanted, someone could probably do it for you if you find nothing to work quit right.

Good Luck