Obvious Pairs (Naked Pairs), Explained

Six cells in this block are still open, and their notes are already written in. None of them shows a single color, so there is nothing to place yet. Look at how many dots each cell shows, because the shortest notes are where a pair hides.

The first two cells of the top row show exactly the same two colors: Yellow and Dark Green. Nothing else fits in either one, so one of these cells must be Yellow and the other must be Dark Green. Which is which is still unknown, and you will not need to find out.

That pair locks Yellow and Dark Green into those two cells. No other cell in this block can be either color, so Yellow comes off the other four cells, and Dark Green comes off the one other cell that shows it.

The cell beside the pair was showing Yellow and Dark Blue. With Yellow gone, only Dark Blue is left, so place it. The Dark Blue note below comes off as it lands. The pair itself is still undecided, and that is the point. An obvious pair does not fill its own cells. It frees the cells around it.