Rocket module; does anyone know what the module icon color's mean?

Rocket module; does anyone know what the module icon color's mean?
I have many green and many purple...and all the final speak bubble are still grey. 

I think you are talking about the completion indicator for tests and modules.  The color indicates how well on average you marked yourself.
Green = mostly easy
Purple = on average, good
Yellow = on average, so-so
Orange = on average, poor
Red = on average, hard
 

hmmm, thanks for your reply... that makes sense...

The icons are in the upper right corner;
a headphone,
a pen,
a lightbulb
a tick
a speech bubble. Which is always grey no matter how many times I try. Not sure why though. 

The icons in the upper right corner are grey until you complete all the phrases in the corresponding section after which they turn green. Clicking on one of those icons will take you directly to that part of the web page.
 

On the old system, after a certain point in working through a test the icon would change color based on how well you were doing, even though you weren't finished. I like the new system better since it stays grey until you are completely finished, which helps you keep track of where you are in the module. 

Ok. Yeah, that makes sense...hmmm but for some reason the last icon - the speech bubble -never changes color regardless how many times I complete "Play it" exercise. Anyway all good. Now worries :) thanks.