Which GUI can have indefinite loop ?

[jst]

It's because you have this all in one line
EURCHFcolorlabel=tk.Label(root, text="-").place(x=115,y=5)

Separate it and it will work.

import tkinter as tk
import time
  
root=tk.Tk()
root.title("COLOR CHECK")
root.geometry("300x500")
 
EURCHFlabel=tk.Label(root, text="EURCHF").place(x=5,y=5)
  

 
EURCHFcolorlabel=tk.Label(root, text="-")
EURCHFcolorlabel.place(x=115,y=5)
EURCHFcolorlabel.config(text='Blue', fg='blue')

root.mainloop()

Thank you, it worked.