NCS S 4030-R20B

The letter S stands for standardized color, meaning that it is a fixed and pre-defined color in the NCS system.

The first number 4030 indicates the blackness and chromaticness of the color.
The higher the number, the darker and more saturated the color is.
In this case, the color has a moderate level of both blackness and chromaticness.

The letter R stands for red, which is the hue of the color.
The hue is the dominant impression of a color, such as red, yellow, green, blue, etc.
NCS has 40 different hues that are evenly distributed around a color circle.

The number 20 indicates the nuance of the color, which is the proportion of the two closest hues on the color circle.
In this case, the color has 20% of blue and 80% of red in its nuance.

The letter B stands for basic color, which is the closest color on the NCS color triangle that has the same hue and nuance as the color.
The basic colors are white (W), black (S), yellow (Y), red (R), blue (B), and green (G).
To summarize, NCS S 4030-R20B is a standardized color that has a moderate level of blackness and chromaticness, a red hue with a slight touch of blue, and a basic color of red.
Visually, it is a dusky purplish-red color that can be seen in some flowers, fruits, or fabrics.