IntGrid layers are grids of Integer values (ie. 0, 1, 2, etc.). Each value has an associated custom color.
How to use them
Open the LAYERS panel 
Create an INT GRID layer 
Optionally, you may adjust settings or add values 
Use LEFT click to draw 
Use RIGHT click to erase 
Hold SHIFT + click and drag to draw a rectangle (right click to erase) 
Use SHIFT + a single click to fill an entire area
