A practical way to narrow down hair colors

[Liamdync]

I tried taking a few phone photos to understand my undertone before changing my hair color. The same face looks warmer by a window in the evening and cooler under a bright bathroom light. That makes the result feel less certain than the tidy labels on the screen suggest. I am starting with light brown hair and only want a modest shift in tone. I found skin tone analysis while looking for a way to compare images, but I still need a sensible way to use the information. I want a shade that works in normal daylight rather than one that looks good only on a phone screen. I can take pictures with the same plain background, no beauty filter, and my hair pulled away from my face. Would indirect daylight and a neutral shirt make comparisons more consistent? I am also thinking of holding a few fabric colors near my face rather than deciding from a single photograph. I could ask the stylist to check physical swatches beside my face and existing hair. That would give us something concrete to discuss instead of trying to prove that an app assigned the right season. I would keep the comparison photos unedited so the colors are easier to judge. If your photos gave conflicting undertone clues, how did you decide whether to try neutral or cool hair color?