ANSI colors cross platform
First off, "cross platform capability for ANSI color printing" doesn't quite make sense (if I understand correctly). ANSI color printing is only going to work on terminals that are ANSI compatible.

Therefore, it doesn't really matter what OS it is: if it's an ANSI terminal, you can use ANSI colored output.

Therefore, you can remove the checking of the operating system.

Note: according to this answer, 


  "All modern terminal emulators use ANSI escape codes to show colours
  and other things."




Judging by the name of the method your presented and the context of the code, you have created a separate method for each color.


This sounds like you are repeating yourself a lot.
It's not very flexible for the code that is using your library.


I recommend that you create a single method print_color_string that takes a string and the color to print.

def print_color_string(str, color):
    ansi_color = getattr(Fore, color)
    if ansi_color:
        sys.stdout.write(ansi_color + p_str + Fore.RESET)
    else:
        # throw error because color is not a valid color