The honest answer: there's no magic bulb that shows you a colour's "true" self, because paint has no true self — it only ever looks the way the light makes it look. So the trick isn't finding the perfect bulb, it's testing under the bulb you'll actually live with.
Two numbers matter. Colour temperature (measured in Kelvin) controls warmth: 2700K is warm and yellow-leaning, the cosy tone you want in a living room or bedroom; 4000K is a cleaner neutral white suited to kitchens, bathrooms and home offices; anything 5000K and up is harsh, clinical "daylight" lab light and best avoided in the home. CRI (Colour Rendering Index) is the one most people miss — it's how faithfully a bulb reveals colour, scored out of 100. Cheap LEDs sit around 80 and flatten subtle tones. Buy CRI 90+ (sometimes sold as "high CRI") and your samples will read honestly.
Here's where bulbs catch people out. Soft, chalky greys and off-whites are the most light-sensitive paints going. Farrow & Ball Cornforth White and Skimming Stone can swing distinctly pink under a warm 2700K bulb, while Pavilion Gray holds its cool composure better. A green like Little Greene's muted tones will deepen and grey-off under low warm light. None of that is a fault — it's just the paint doing its job.
Practical method, mate: paint a big sample board (A2 minimum, two coats), and view it under your actual room bulbs at the times of day you use the room — morning, dusk, and lamps-on at night. Don't judge a colour under the showroom's white spotlights and assume it'll behave at home. If you're matching to existing decor, view both side by side under the same source.
Swap any sub-90 CRI bulbs before you commit to a colour. It's a couple of quid and it stops you specifying something that looks dingy every evening.