Updated CSS and javascript

CSS: fixed pop over so it stays full when scrolling down the page.
JS: Wrong use of css() and show() in if statements, fixed to use toggle
instead, you could use the check then fadeOut, and slideDown.

The correct use of to check that an element is visible would be $elementselected.is(':visible')

Although it works (I'm not sure how) if you check the results for $colourOverlay.css("display", "none") it does not return true (use console.log($colourOverlay.css("display", "none")) before the if statement to check value)