In this demo page, accessibility toolbox opens when you click the button on the middle.

You can change the button colors, position as you desire from module backend.

Only  Dyslexic Readability button and Grayscaler  - I changed the description text and the header text

You can set every button hidden or shown.

You can also see other demos 

The text and the images are for demo....

Image to text contrast levels and  grayscaler.