That you for sharing the pictures, that does clear it up. That is what I would call red (the scale behind it makes it look a bit purple, but it's red) and means your alkalinity is zero. That's bad as it means your pH is off-the-scale low and potentially doing damage to your pool and equipment.
Any chance this is a new plaster pool? If not then this needs corrected ASAP. Adding enough baking soda to get the TA up to 50 ppm would be a good start, then retesting after a couple hours to make sure the TA and pH have increased.