Answer: black
Step-by-step explanation:
A colour filter is a filter that lets only one colour pass through it. For example, a red filter lets only red colour pass through it, while a green filter lets only green light pass through it.
In this example, we have a red and blue jacket. At first, we put a red filter: this filter lets pass throuhg only the red light. Then, we put a green filter: this filter lets pass only green light through it. However, there is no green light coming from the previous filter (since only red light passes through it), so the jacket appears black (no colours).