['red', 'black', 'white']
['red', 'black']
colours = ["red"]
for i in colours:
if i == "red":
colours += ["black"]
if i == "black":
colours += ["white"]
print(colours)
colours = ["red"]
for i in colours[:]:
if i == "red":
colours += ["black"]
if i == "black":
colours += ["white"]
print(colours)