These are questions about digital painting in general

I am new to it and noticed that normal blends give a grayish color, like so:


Why does that happen? What is technically happening in digital and traditional medias that makes them look so different?

And how can I achieve a blend that averages the levels of dark and light and just "slide" the color wheel to make them look like this?

It still isn't what happens, as seen above, but is more satisfying. In fact, the digital normal mode bleding is closer to the color, but it's white and black are off.

The difficulty of blending is something that makes the adaptation to digital seem very difficult for me.

While I'm not much of an artist, and certainly not very familiar with all of the ins and outs digital painting sofware like Krita, I am fairly familiar with how colors work in light and software.

I think the main difference is the color space involved. Traditional painting with pigments generally uses Red, Yellow and Blue as the primary colors, while digital images use Red, Green and Blue as the primary colors. Some digital image software supports mapping between RGB and CMYK (Magenta, Yellow, Cyan, Key) which can result in color values which more closely approximate how much of each pigment is used when printing.

One thing that stands out in your examples is that while in traditional painting Yellow and Blue are neighboring primary colors and Green is the secondary color between them, in digital painting Yellow is a secondary color between the primary colors Red and Green and directly opposite to Blue. (there are also some nuances about the exact blues involved as the primary color blue that you would use for traditional painting is usually (cyan which is) greener than the primary color blue used in digital images).

As for how blending itself works, digital blending usually uses the average of the RGB values. You can envision that as a hexagon where the points of the hexagon are the colors Red, Yellow, Green, Cyan, Blue and Magenta. The blending takes the two colors as endpoints of a line in that hexagon and then selects colors along that line between depending on how strongly one or the other is used. When the two colors are on opposite sides of that hexagon then the average will tend to be very gray.

An alternative way to tell if two colors are opposites according to the RGB model is to compare the Hue values. Hue measures where on the color circle the color lies, with values from 0-360. If two colors have Hue values which differ by 180 then they are opposites and the (rgb) blending will pass through gray.

At least that's the way blending works when using RGB (or CMYK) color space. I believe you may get different results by using HSV, HSL, or other color spaces which may preserve the Saturation (i.e. going around the circle rather than through it). Unfortunately I'm not very familiar with Krita and how to configure some of these kinds of things.

The simple answer is that you're working with a new and different set of tools and materials that have different characteristics to the traditional tools and materials that you've been used to. It will take time to get used to them.

The characteristics of digital painting are because of the numerical methods that involve mathematical operations on sets of numbers that represent the colours. This is a complicated and confusing subject area.

On a practical level, the traditional skills of paint mixing are not really required (in theory) because you can choose any colour/shade/lightness/saturation that you want from around the colour wheel and inside the colour triangle. (Subject to the limitations of the colour space, your computer monitor and your printer.)

If you're working with two particular shades of orange (as an example) and you want an intermediate shade, one good way to do this is to use the Geometric Mean blending (this is in the Mix group of blending modes). To my (non-artist) eye, this seems to give good intuitive results. Then you can colour pick the intermediate shade and mix it with one of the original shades to get closer to either of them, etc. You can use a blank area of canvas or go off-canvas to do your mixing. Or use a separate layer for mixing experiments. The simple blender brush preset seems to give the same results as the Geometric Mean blending mode.

These results only seem intuitive if you mix two colours that are close to each other on the colour wheel. If you mix blue and yellow, you can get shades of grey or dark green or even dark red depending where exactly the 'blue' and 'yellow' are on the colour wheel. If you mix blue and yellow with the Addition blending mode, you get white.

I suggest that you experiment with the different blending modes to see what effects they give you.