Need advice before changing my hair colour

Last weekend I quietly cleared the clothes I never wear from my work wardrobe. I have fair skin, naturally blonde hair, and clear blue eyes, so I expected the remaining pieces to work together fairly easily. Instead, anything close to mustard makes me look slightly sallow, especially under the lights in our office. Colours such as gentle greys seem calmer, although I cannot tell whether that is a real pattern or simply preference. A recent photo in a slate-blue shirt made the difference noticeable enough that I want a sensible method before choosing a work capsule. I keep wondering whether I am reacting to the shop lighting. To see the colours side by side, I used soft summer hair colors as a calm second opinion. Now I plan to compare the same two tops in video calls before choosing between a blue dress. I am trying to keep the experiment cheap, repeatable, and practical. Is there a simple comparison that separates undertone from hair colour?