Yes, and anyone who tells you otherwise hasn't lived with a tester patch for a week. The paint isn't changing — the light is. Colour is just light bouncing off pigment, so when the light shifts, the colour you see shifts with it.
Here's the daily cycle. Early morning light is cool and bluish, which makes greys and off-whites look crisper, even slightly steely. Midday is the most neutral — closest to how the manufacturer's swatch was photographed. Late afternoon and evening daylight turns warm and golden, pulling pinks, yellows and reds forward and making the whole room feel cosier. Then the sun goes down and you're under bulbs, which is a different game entirely.
This is exactly why complex greys play tricks. Farrow & Ball Cornforth White and Skimming Stone can read clean and grey at midday, then warm up and even look faintly pink by evening — that's the underlying pigment doing its thing as the warm light brings it out. Pavilion Gray holds steadier but still cools off on a north-facing morning. A warm white like Farrow & Ball Slipper Satin glows beautifully at golden hour but can look a touch creamy under cool morning light.
The "but what about" question: *which time of day is the real colour?* None of them — they're all real. What matters is when you use the room. Painting a north-facing bedroom you mostly see at night? Judge your tester under your actual evening bulbs, not at noon. A kitchen you live in all day? You'll need a colour you can live with across the whole range.
Practical advice: paint two coats on a big bit of lining paper — at least A2 — and move it around the room. Check it morning, midday, evening, and under your lamps. Live with it three days minimum. Cheap test pots and ten minutes of staring will cost you a repaint.