How does Illustrator calculates tints?

I once needed to parse color values from a spot tint. As I understand it, it uses linear interpolation from white to the original color. I wrote a note about this with a code example: https://aiscripts.medium.com/get-spotcolor-tint-color-b699f569c03d

Lukas,

The R, G, and B, are components of colours made of light. With the value 255 of all you have white, white light made of all the colours; with the value 0 of all you have black, the lack of light from any of the colours.

Tints correspond to Opacity; you can compare a 20% tint and a 20% opacity (Transparency panel) on a white background.

You can also compare the greyscale % values such as 25%, 50%, 75 % to the appearance of equal values of R and G and B such as 192, 128, and 64.

When you start out with such different RGB values as 0/47/147 and reduce the tint, each of the R an G and B will grow at different rates and get closer to one another; the R values grows the most (starting from 0), and B grows the least (starting from 147 which is more then 50%/128).

To go a bit further, you can:

1) start out with a rectangle having a fill of full red 255/0/0 as a global colour, then make copies of it with tints 75%, 50%, 75%, and 0% vertically up or down,

2) Make two copies to the left of the whole set,

3) In the first copy set, switch from the tint to RGB and see how the G and B increase from 0 to 255,

4) In the second copy set, switch from the tint to HSB and see how the S decreases from 100 to 0.

Concerning HSB, the H is Hue, 0 being pure R (you can also see pure G and B), S is Saturation, and B is brightness.

And you can look here,

https://helpx.adobe.com/illustrator/using/color.html