@Michael
That magenta is good for mixing purples/violets.
To mix vibrant secondary colours (orange, purple, greens), you should mix them with primary colours that are close to the secondary colours on the colour wheel.
In this case, magenta is closer to purple than that red. ArtGraf has only one blue which looks like a Cobalt Blue (somewhat neutral blue). Ideally to get a vibrant purple, you'll want to use a warm blue (eg ultramarine) which you can see is close to purple on the colour wheel.
As for Phthalo Green, it's good for mixing dark greens. Eg. leaves, plants, parts of trees that are in shade. All Phthalo colours are good for mixing darks. There's no Phthalo Blue in the primary 3-piece set so mixing a dark black would be impossible. Another use for Phthalo is to mix with red/magenta to produce greys/black.
Not being able to mix dark black is not that big of a deal for pen, ink, watercolour sketches because you may want the line art to be the focus. See Lapin's sketches.
@Michael
That magenta is good for mixing purples/violets.
To mix vibrant secondary colours (orange, purple, greens), you should mix them with primary colours that are close to the secondary colours on the colour wheel.
In this case, magenta is closer to purple than that red. ArtGraf has only one blue which looks like a Cobalt Blue (somewhat neutral blue). Ideally to get a vibrant purple, you'll want to use a warm blue (eg ultramarine) which you can see is close to purple on the colour wheel.
As for Phthalo Green, it's good for mixing dark greens. Eg. leaves, plants, parts of trees that are in shade. All Phthalo colours are good for mixing darks. There's no Phthalo Blue in the primary 3-piece set so mixing a dark black would be impossible. Another use for Phthalo is to mix with red/magenta to produce greys/black.
Not being able to mix dark black is not that big of a deal for pen, ink, watercolour sketches because you may want the line art to be the focus. See Lapin's sketches.