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Out of nowhere my pencil tool has been randomly changing color to that of my bg color even when it's not selected. Pressure sensitivity isn't the case, or brush options, I've reset the brush preset, and even the CTRL-ALT-SHIFT open photoshop method. 
Here are an assortment of brush strokes, at random they turn into the background color. This only happens to my pencil tool, the brush tool works just fine
Try turning off Auto-erase in the Control Bar across the top of the screen.
Auto-erase is a Pencil Tool option which tells the tool to use the background color if a new stroke is started on top of the foreground color.
Note that the very top tip of all the red strokes..... start on top of an area with the foreground color.
