Color 4K-X (Bullet) Or Color 4K-T (Turret) are 8MP/4K cameras. Same series different form factor.They have 1/1.2" sensors.
They DO NOT have nor can they see IR.
They have white light LEDS to help add light to a scene that needs it.
If you have enough light, you may not need to run the LEDs
Nighttime color is possible with most ANY camera, it just depends on how much light you have and how big the sensor is, ie; how well it picks up light.
The better 4MP cameras are the 5442 series,.
They have 4MP 1/1.8" sensors (smaller)
They do very well at night and come with IR lights and can see
IR light. So if there isnt enough white light in a scene to run color, you can switch to B&W/IR
Generally speaking the 4K series can pick up light a bit better than the 4MP 5442 series, but there are tradeoffs.
As mentioned, ANY cameras (well most) can run "color at night"
The trick is to do so and get a crisp image and not a big motion blur blob.
Just because you can run a camera in color at night doesnt always mean its a good idea.
Broadly speaking, to reduce motion blur at night in color mode, you need
A) a buttload of light and
B) a shutter of min 1/60 and preferably 1/120 (or if you have enough light, 1/250 is even better)