First, let's look at Susan Collins during a budget hearing for the Department of Transportation:
Senator Collins went for the classic red jacket look. This warm red color works for her coloring, and she wears it frequently. She stands out behind her microphone, even with the staffer in a busy print behind her. The important thing to remember here is that this jacket works for her. The same exact outfit on someone else might not.
Now let's have a look at Claire McCaskill in a floor speech on discretionary spending:
Senator McCaskill has made modifications to the classic red jacket look. She went for a jacket that is longer and unlined, making it less structured, and layered it over a darker red print top. The length of the jacket and the color variation both help to create a longer body line. Try to imagine Senator Collins's jacket on Senator McCaskill. Doesn't really work, does it? So much structure would make her look boxy.
Don't ever imagine that you "can't" wear a particular color or style or fabric. You just have to find the right shade, the right combinations, the right pieces to make it work for you.