Illustrator CC, Cut An Object & Edit Color

Greetings all,  I have run into an issue that I cannot find an answer for.  I am hoping someone can help.  I will do my best to describe what I am trying to do....

I have an SVG of an American flag.  It is a waving flag, with several stripes overlapping.  This has resulted in the image having two major parts.  The main section consists of the the star field and a number of stripes, with the smaller section consisting of the lower stripes.  If I try and color the star field blue, it causes the stripes associated to also turn blue.  I used the knife tool to "cut" the top stripe and am able to separate it from the star field, however, they remain "associated" with each other, so when I change the color of the stripe, it also changes the color of the previously attached portion of the image.

My question is, how do I cut the stripes (where they join the star field) and be able to edit the colors independently?

I am using Illustrator CC 2017.

Thank you in advance for any guidance!

Warren