Label and Editor not visible in black ground in Mac OS,

Code
from tkinter import *
def main():
root = Tk()
root.geometry('500x500')
num = StringVar()
l1=Label(root,text='strike',highlightbackground="Yellow", fg="Blue", highlightthickness=30)
t1 = Entry(root,textvariable=num, highlightbackground="Yellow", fg="Blue", highlightthickness=30)
btn=Button(root, text='Click Me', bd='50',command = startorder, highlightbackground="Yellow", fg="Blue", highlightthickness=30)
l1.grid(row=0,column=0)
t1.grid(row=0,column=1)
btn.grid(row=1,column=0)
root.mainloop()