Elusive Spots

Look at the color grids above. Start from the red one. Do you see the light red spots at the crossroads between the red squares? 

Now look at the blue grid. Do you see the light blue spots blinking like those red ones? 

Finally take a look at the green grid. Can you see all those flickering light green spots?

Are there really any spots between the squares, and why do they only blink and try to disappear when you want to stare at any of them?