main.py

#!/usr/bin/env python
"""Make the text green/red if mouse is on the left/right of the window."""
try:
    import tkinter as Tk
    import tkinter.ttk as ttk
    import tkinter.font as font
except ImportError: # Python 2
    import Tkinter as Tk
    import ttk
    import tkFont as font

def on_mouse_motion(event):
    mouse_on_the_left = event.x < widget.winfo_width() // 2
    widget['foreground'] = 'green' if mouse_on_the_left else 'red'

root = Tk.Tk()
root.title('Name')
root.geometry('400x400') # set window size
text = Tk.StringVar()
widget = ttk.Entry(root, textvariable=text, font=font.Font(size=36),
                   justify='center', state='readonly')
text.set('B') # set text
widget.pack(expand=True, fill='both')
widget.bind('<Motion>', on_mouse_motion)
root.mainloop()