Lateral marks
Am I going towards the coast?
In group A countries, when one comes from the sea towards the coast, s/he leaves the red cylindric lateral marks on portside and the green conic ones to starboard. Note than in the Americas, group B countries, the colour are invereted, but not the shapes... See more on lateral marks here.
In Sweden, particularly when sailing along the coast, in the inner archipelago, it is getting hard to know if you are going towards the coast of not. Therefore, Swedish maritime authorities have implemented a rule stipulating that, in the fairway going around Sweden, anticlockwise, from Svinesund to Haparanda, red marks will be placed on portside and green ones on starboard. As soon as the fairway departs toward a harbour, group B country rules apply.
It sounds straight forward, but can create ambiguous situations.
Let's consider few situations. You sail from a, through b, to c. In position a, you are on the circular fairway, and therefore, red marks are to be left on the side of the coast, on your starboard side when coming from the north, meaning goind around Sweden on a clockwise path. Same situation in position b. But then, when going from b to c, you are entering a fairway going to the coast, and then you should let the now on red marks on your portside. If you go from b to d, you are continuing in the fairway belt and therefore red marks should continue to be left on your starboard, along the coast. Finally, if you go from b to e you are quitting the circular fairway and sailing towads the coast and its habours. Red marks should be left on your portside.
As a rule of thumb, always check in the nautical charts the type of fairway you are engaging, and verify each section in case it would change of nature...