To find the most common thing, combine the counting pattern with "biggest so far":

votes = ["red", "blue", "red", "green", "blue", "red"]
counts = {}
for v in votes:
    counts[v] = counts.get(v, 0) + 1

winner = None
for colour, n in counts.items():
    if winner is None or n > counts[winner]:
        winner = colour
print(winner, "wins with", counts[winner], "votes")

(Python's collections.Counter does all of this in one line. You will meet it in Unit 19, and it is far more useful once you know what it is doing.)