But it seems to me that mixing complements can also be visual complements
I think you are thinking that visual complements would be any pair that are visually pleasing to look at such as this flower, and thus mixing complements could also be visually pleasing
and that is very true. But for understanding what and why they are separately what they are, I think it would be good to get a handle on theory regarding color in light
, which is optical and exhibits additive mixing vs pigment color
which is physical and exhibits subtractive mixing. Here is a good page
that explains the two.
This monitor is using additive mixing, if the red, green, and blue lights are mixed then they add up to making white, which is made of all colors. you will see that when you mix red and green light together, the result is yellow light. Now if you mix yellow light with blue light (yellow and blue being visual complements) you will get white. (think visual complements here)
The paint on your palette is using subtractive mixing, if cyan, magenta, and yellow are mixed then they diminish or subtract from each other to make a dark black/gray, which is made of no color. (think mixing complements here)
So for purposes of theorist, complements for mixing are one thing, complements that you look at visually are another. For us art lovers, any combo that looks good to us is "complementary".
It is really a lot to explain and so I think it would be good to visit our color theory forum with Einion and other experts there who can lead you on better than I can. Actually this thread should probably be in that forum where I think you would get a lot more response. For instance, here is a thread
in theory about visual complements.
This is not to say that to paint good paintings one must learn and apply color theory, in fact, I believe to paint well that it is very acceptable to ignore color theory altogether and paint with your heart and your own feelings.
For instance, take the concept of warm and cool colors as it has been mentioned earlier by myself and the other posters. Well in color theory, there is nothing but disagreement and confusion about just what it is, just check it out sometime, but within the artists' own perception, there is no confusion and artists have and will always think in terms of warm and cool feelings when painting.