NSR (and to a lesser extent ScaleAuto) has released several types of chassis. The colors differ in appearance, but the stiffness differs in terms of usage.
By the way
Soft: Blue Medium: Black Hard: White Ultra Hard: Green Ultra Light: Yellow
That's how it is.
So, when should you use them differently?
According to the NSR technical guide, different wheels are used depending on the grip level of the track.
... apparently ...
Blue: Carrera (Scalextric)
Black or white: NINCO (Policar)
Green: Wood
(The text in parentheses has been added. I have not actually seen ScaleAuto, so there is no mention of it.)
The intention seems to be to make the chassis softer on courses with low grip levels, taking advantage of the flex to prevent loss of traction.
The motor mounts also have different hardness levels.
The official stance on this seems to be , "It's a personal preference (how you drive, etc.), so try out different things and decide."
I actually tried a few of them,
Classic, Formula is soft,
On the Abarth 500 the Ultra Light worked very well.
(This is my personal opinion)
When we think of traction (grip), we tend to think of tires and suspension, but
The chassis also has a big impact (although only the NSR can be replaced),
It's interesting to see how the quality of the ride changes when you replace them.
"Changing the chassis (floor)" sounds a bit like F1 and makes me feel a bit excited (laughs).