Beginners help in Illustrator - change color object

Saying short, it's a result of tracing images.  When you trace with automatic settings for a color image, the program creates some artifacts, small objects with different unneeded colors, opacity settings etc. You can see them in Outline mode (Ctrl/Cmd+Y).

next time will be better to trase such images with "3 colors" setting, it provides more clean result.
What you can do now:
1. Return to Preview mode (Ctrl/Cmd+Y).
2. Select only the needed details

3. Use the first button on the Pathfinder panel (you can find it in the Window menu):

4. The result will get the color of the top of selected objects (in your case, it's the small dark blue artifact on the leg of the character) and come to front. It's OK.

5. Now use eyedropper to take the color from another character, and send the object to back (Ctrl/Cmd+Shift+[)

6. finally, would be good to clean the image. For example, you can select all white objects with Magic Wand, deselect internal ones (faces, hands etc.) and delete the outer ones. Maybe it's worth to unite the colored elements, especially dark blue ones, and set them the same color. Did you notice that you have 2 different colors on the ball's face, they are not the same as the characters' outline, and all the letters have also different colors? 

To use this image as a logo, you need to rid all the artifacts (delete or unite) and set just limited set of colors. As far as I can see, there might be 4 colors: 
- dark blue for main outlines and silouettes
- another dark blue for the ball's face
- light blue for caps and shirts
- greenish light blue for caps and shirts.
Make sure that all the objects have just one of these colors for good consistency of your logo and style.