Look at column 5 of the puzzle. Cells B5 and E5 are highlighted in blue. Both of these cells contain the same two candidates, namely 7
and 9. Although we can't say at this stage which cell will contain the 7 and which cell will contain the 9, at least we can say that none
of the other cells in column 5 can can have either 7 or 9 as a solution. So, referring to the candidates highlighted by a magenta background,
we can say that C5 cannot have a solution of 9 and H5 cannot have a solution of 7. These two candidates may therefore be removed.
Naked pairs may also appear in rows and boxes.