You approved the brand color on your monitor. The client saw it "way too purple" on their phone. Nobody is wrong, and nobody's screen is broken — a HEX code is a recipe, and every display is a different cook.
#2563EB says precisely one thing: mix red at 37/255, green at 99/255, blue at 235/255. What it cannot say is what those primaries look like — and the red an OLED phone can produce is measurably different from the red of a five-year-old office LCD. Wider-gamut screens produce more saturated primaries, so the same recipe comes out more vivid. This is why designers who care about print pay for hardware calibration; the rest of us live with the spread.
1 – Night mode. After sunset most phones pull the whole display toward orange. Your carefully-chosen cool gray is, at 10 pm, warm. Every color judgment made under Night Shift is a judgment about a different color.
2 – Brightness. A dim screen crushes dark shades together — the difference between #111 and #222 exists at full brightness and vanishes on battery-saver. This is also why the contrast standards feel strict on your bright monitor: they're budgeting for the dim one.
3 – Vendor "vivid" modes. Many phones ship in a saturation-boosted display mode by default. The natural/standard setting exists — buried in display options — and it's the honest one.
4 – Ambient light. The same screen at the window and in the basement produces the same photons into completely different eyes. Human white balance adapts within minutes; you don't notice until you compare.
Everything above applies twice to the detector's camera mode — once in your phone's camera (auto white balance guesses what "white" is in the scene, and edits every color to match) and once on whatever screen shows the result. That's why the tool tells you plainly: photos and screenshots read exactly, live surfaces read as lit. It's also the cheap trick for better readings — sample in daylight, not under the kitchen's warm LEDs, and the camera's guess gets much better.
Codes, not adjectives, in every handoff — "too purple" starts arguments, "#4C66C9 on my screen" ends them. Judge color at full brightness with night mode off. And when a color must match across a team, one person reads it in one lighting condition and everyone else works from the number. The number is the only thing every screen agrees on.