Can't get tkinter button to change color based on changes in data

[Larz60+]

Here's an example class that uses trace_add:

from tkinter import *
from tkinter import ttk


class TryTraceBack:
    def __init__(self, parent):
        self.parent = parent
        self.parent.geometry("200x130")
        self.parent.grid_rowconfigure(0, weight=1)
        self.parent.grid_columnconfigure(0, weight=1)

        self.var = StringVar()


    def validate(self, var, index, mode):
        print(f"Traced variable {self.var.get()}")

    def CreateWidgets(self):
        # registering the observer
        self.var.trace_add('write', self.validate)

        frame = Frame(self.parent)
        frame.grid(row=0, column=0, sticky="NESW")
        frame.grid_rowconfigure(0, weight=1)
        frame.grid_columnconfigure(0, weight=1)

        label = Label(frame, textvariable = self.var).grid(row=0, column=0, sticky='EW')

        entry = Entry(frame, textvariable = self.var).grid(row=1, column=0, sticky='EW')


def main():
    root = Tk()

    ttb = TryTraceBack(root)
    ttb.CreateWidgets()

    root.mainloop()


if __name__ == '__main__':
    main()