# gradient_color_arc.py

# gradient_color_arc.py

import tkinter as tk
root = tk.Tk()
width,height=400,220
d=str(width)+"x"+str(height)
root.geometry(d)
canvas = tk.Canvas(root,width=width,height=height)
canvas.pack()
x1,y1,x2,y2=25,30,370,370
arc_w=40
def my_upd(d):
    change=int((255/180)*d) # increment in colour value
    color_c='#%02x%02x%02x' % (255-change, change,0)
    return color_c
res=1 # resolution or steps
for d in range(0,180,res):
    canvas.create_arc(x1, y1,x2,y2, start=d, extent=res+1,outline=my_upd(d),
        width=arc_w,style=tk.ARC)
root.mainloop()