It is possible to print a locomotive like this using a 3D printer?

yes, but you won't have that level of detail.

For example, here is a 3D printed train.

Or it is better to print using white filament and then hand paint?

If you want fine details, you will likely have better results painting. 3D printing is usually limited to a few colors 2, 3, maybe 4, in some extreme cases 16. Color adds a lot of time and material waste to a print. For example, a print that takes 1 hour with one color may take 2,3 or even 4 hours when using muiltiple colors. If the print takes 30g of filament, multi color can take like 150g due to purge waste.

I would recommend a Bambu printer, that's what I use. There is zero assembly and it just works, very minimial problems provided you don't get a lemon. It can also do multiple colors with AMS units.

Here's a cool example of what you can do with just a single color printer.

https://www.reddit.com/r/3Dprinting/comments/18sy3g4/p51_mustang/