The correct pronouns to complete the sentences are "it" and "that."
So the completed sentences would read: "Our garage, it has rust spots, needs to be painted. The people next door painted their garage a bright yellow color that we like very much."
However, the first sentence could also be phrased more clearly as "Our garage, which has rust spots, needs to be painted." If the provided options did not include "that," please let me know which options you could choose from!