Which color fan to buy or unnecessary?

By "buying" a house I mean that we are buying a prefabricated house. For a solid house I would speak of "building" a house. I learned the difference from one of the forum members here and find it pretty clever.

But a prefabricated house does not come to your plot by truck, or have you ever seen a house being driven around? So are you looking for a prefabricated house or a finished house?

First, make sure you know exactly what you really want: buy, build, prefab house or solid construction. The fact that there is a difference between all of these is already stated by the Duden...

or also there (in the same thread, post #11:

The problem there is the different materials.
Window manufacturers, i.e. carpenters, have color charts with the texture of the surface, for example.

By "buying" a house I mean that we are buying a prefabricated house. With a solid house I would speak of "building" a house. I learned the difference from one of the forum members here and find it quite clever.

You are confusing something: if you are the builder yourself, you build a house. Better yet: you have it built. Whether solid or timber frame construction. Regardless of whether with a general contractor or architect. With a contract for work, it is built. And exactly how you want it.

If you have concluded a purchase contract with a developer, then you buy a house. With luck you are allowed to make changes to the design or influence the equipment. But the builder remains the developer.

that we buy a prefabricated house

Then at the latest, during the selection appointment, a color fan will be held in front of your nose. Everything up to HBW xx is included, from xx to xx costs an extra xxx€, above that an extra xxxx€. There you choose something. It makes absolutely no sense to decide on a color now beforehand (without knowing the provider's offer and the associated extra price list).

Better take a look in new residential areas to see what you might roughly like and roughly settle on a color family. That is enough.

Color swatches as sampling aids are anyway a crutch for colorblind people, which will regularly lead to disappointments: even with practice, color harmonies can only be estimated unreliably by holding together four-square-centimeter color fields; and as soon as a glossy lacquered smooth surface is adjacent to a matte coarse-grained texture, it is basically a comparison of apple juice with pear jelly. This combination is regularly most disappointing when "tone on tone" or "seamless transitions" are desired.

One can of course willingly surrender to their fate, or do something about it. The color fan is suitable for that. The mini version is not bought, so a comparison is also possible.