The absolute color of the pH test might look different under different color temperature of light, but the comparator should be affected the same by the lighting condition. Anyway, if you think a standard light will help then that's all that matters.
As for the CYA test, that will be affected by the intensity of the light, but not the color temperature. So for that at night you need strong indirect light which means a LOT of light indoors not shining down into the tube but indirect all around it (coming in from the sides at all angles.
As for the CYA test, that will be affected by the intensity of the light, but not the color temperature. So for that at night you need strong indirect light which means a LOT of light indoors not shining down into the tube but indirect all around it (coming in from the sides at all angles.
