Dynamic Color Changing Blocks

We need a HMTL5 <Single Page Application> Solution as follows All users in our office will open a webpage for example [login to view URL] Webpage will break the page down into 4 sections. Each Section will have a background color. A user at one browser can click the button inside the section to change the color The color should automatically change on the other browsers in Realtime (2 seconds max delay) (not via automatic refreshing of the page). This should be accomplished in a manner as to not performing SQL INSERTS/SELECTS or writing to a file and reading from a file, as both of these will result in a loop that is not sustainable as the number of open browser sessions increases along with the 4 blocks increase. See attached rendering. This must be able to be ran on a LAMP installation Should be as small of a footprint as possible. Deliverable should be a step by step guide indicating how to implement this on a LAMP install