Default color is plain white “Flat Pack” material. Alternative is any type of wood, from white sycamore over rustic oak to black ebony. For commercial / industrial gastronomy, the default is stainless steel.

Handles are similarly variable:
Default is metal rods, with their alignment being horizontal when its a drawer that slides out, or vertical when it is a door that swings open.
Colors for metal handles aim either for contrast toward the background or a close match to it. Usually expect steel/silver, gold, brass or burnished metal as colors for metal handles.
In rustic and old school kitchens, handles will tend to be knobs, either plain metal, or in regions rich with far trade, porcelain knobs in the patterns of local or foreign cultures.
Also common are handles made of wood, similar to the metal handles but thicker, or, in the same style but thinner than the wood ones, plastic handles.

GKMS compliant components are placed beside each other and then a work surface is placed on top.
On cabinets and fridges, that is usually a wooden board of 5cm thickness. This can also be a real stone slab or a metal element or a simulacra made by a coating of robust plastic with the desired pattern over a wooden core.
Ovens often come equipped with 5cm thick Stovetops, where the cooking pots can be placed.
On cabinets with drawers, the top drawer can be a fake one because there's a kitchen sink on the cabinet. The sink modules are also 5cm thick, so no matter if workplace, stovetops or sink, all surfaces are at the same height of 85cm above the ground.

Also, all doors and drawers start only 10cm above the floor, so that opening a door or drawer does not collide with ones feet.
Actually those lowest 10cm are even drawn back 5cm from the cabinets front, as not to stub ones toe when stepping close to a worksurface.
German workplace safety and engineering!