For close colour work, ignore raw lumens and look at CRI (colour rendering index) and colour temperature. You want CRI 90 or above, ideally 95, and a neutral white around 4000K–5000K. Cheap LEDs often have a harsh blue spike that flattens reds and greens, which is exactly the navy-vs-black problem TinyAwl described.
I’ve used several neck lights for embroidery and fly tying. The one I keep on my workbench has two adjustable goosenecks, a wide padded band, and a built-in diffuser strip so the LED chips don’t glare directly into the fabric. It has three settings; I usually use the middle one for evenweave and the lowest one for metallic threads, because the high setting creates too much shimmer. Battery life is around six hours on medium, and it charges via USB-C, which matters more than it should.
What I’d avoid: the type with a rigid plastic band and tiny spotlights at the ends. Those dig in behind the ears and create a tunnel of light with no peripheral spill. Also skip the ones with a built-in magnifier unless you already know you want that—you’re carrying extra weight for a lens that may not match your working distance.
If you already have a clamp lamp you like, a high-CRI bulb and a cheap floor stand can solve half the problem for less money. But a neck light is genuinely useful for couch work, guild nights, and anywhere you don’t want to drag a cord.