What is the meaning of colors in activation maps? I am trying to understand how the neural network works. I plotted the intermediate layer activations and I got the following image. 



I used the matplotlib library and selected cmap='jet'. I would like to know what is the meaning of these colors? Does the area with color red mean the filter is activated in that region? Then, what about the green, yellow and blue color means?
In heat maps, generally reddish regions represents higher values where as bluish ones represent lower.