COLOR IT

There are two streets. First street has $N1$ houses. Second street has $N2$ houses. There are no connections between houses inside street1 and also street2. Some houses in street1 are connected to some houses in street2. The houses are colored either red(R) or blue(B) or is colorless (U). Our task is to color connections in between houses in street one and two. To paint a connection red it tak