We’re trying to pick a color to paint our walls. We’ve found a nice soft yellow color that we like. We got a sample jar and painted some poster board and put it up on the wall. The problem is that depending on the light, the color may look yellow, greenish-yellow, tan, peach, or soft yellow. I can understand that the color may look lighter or darker depending on the light, but why is it changing colors? I would have expected it to look darker or lighter yellow depending on the light.
Changes in time of day will change the color temperature of sunlight. Different artificial light sources will have different distributions of frequencies and may be warmer or colder than sunlight. In addition, the pigments in the paint are probably a mix and the light sources may be absorbed or reflected differently. So depending on the angle you’re viewing the paint from, you might see a somewhat different tint.
Finally, other objects in the room may be reflecting colors and affecting your color balance. An obvious example would be if you were wearing a bright green t-shirt while comparing color swatches.