# List with duplicates
mac = ['b4:6d:83:77:85:f3', 'b4:6d:83:77:85:f3', 'a4:6d:83:77:85:f4', 'c4:6d:83:77:85:f3', 'b4:6d:83:77:85:f3']

# New empty list
mac_unique = list()

# Iterate over the list
for item in mac:
    if item not in mac_unique:     # check if each element is already in mac_unique list
        mac_unique.append(item)    # add it if it's not in the mac_unique list

print(mac_unique)