You can help each other by connecting your regions. However, that can only be done indirectly, and takes some teamwork. If you manage it, then you can score significantly more points for your roads and cities. We will use roads as an example of how this works.

This tile, that you just drew, could be placed so that it finishes yellow’s road. However, since yellow is already on that road, you would not be allowed to add a meeple of your own. Instead, you decide to place the tile such that the roads are not directly connected.

On one of your next turns, you draw this tile and add it to the two unfinished roads, joining (and finishing) them. There are now 2 meeples on the road. Since the road is finished, it triggers scoring, where you score 4 points each, i.e. 8 points total. Return the meeples to your collective supplies.

However, it does not matter if there are several meeples of the same color in 1 area. You only get additional points if meeples of different colors are involved in a scoring. You then get for each other color involved again as many points as usual. Of course, this also applies to cities.