Explanation
Here’s the sequence up to the 12th second.
Every time you reach a time divisible by 6, the sequence starts over with W and proceeds: W-B-W-G-W-R. 204 is divisible by 6; hence, starting at the 204th second, here are the light’s movements through the 209th second.
As you can see, the movement from the 208th to the 209th second is from white (W) to red (R).