When painting a scene, you’ll see a riot of colors. The key is to simplify, find the “average” green in your meadow and then add some of the more vivid highlight colors as accents. Find masses for the shadows. Actually, it’s all about identifying masses of distinct color. This can be difficult, and I’m still learning how to do it well, myself.

To determine how to mix colors you see, you need to learn your way around your palette. Try a limited selection of colors, and make swatches of mixed color. Try a “split primary” palette (a warm and a cool each of Red, Yellow and Blue) with white. Let’s say you go with:

Alizarin Crimson Hue (heresy, I know, but real Alizarin is a fugitive color)
Cadmium Red Deep
Cadmium Yellow Light
Cadmium Yellow Deep
Cerulean Blue
Ultramarine Blue

For each of these colors, do a “chart” of swatches. So, for Alizarin, you’ll first do a swatch of pure Alizarin, then next to that do Alizarin mixed with a bit of Cad Red Deep, then Alizarin with a bit of Cad Yellow Light, etc. Each mix should have Alizarin as the dominant color (I do about a 2:1 ratio). For each mix as well as the pure color, you’ll also want to mix varying amounts of white to make a five step value scale.

The result will look something like this.

You can make this even simpler by choosing a single of each primary + white. Anders Zorn famously used white with Cad Red Light, Yellow Ocher and Lamp Black to paint rich portraits.

Choices of “ingredient colors” are much easier to make when the initial number of choices is relatively small. When you place a small, carefully-selected, array of tubed colors on your palette, and use only those from which to choose when mixing colors for the scene you wish to paint, life becomes a great deal easier when the goal is to match your paint colors to those of the reference from which you are painting.

Start with these colors:

Burnt Umber
Ultramarine Blue
Permanent Alizarin Crimson
Cadmium Yellow Light
White (Titanium White is fine)

With very few exceptions, most colors of landscapes (and some still-lifes) can be created by mixing combinations of these colors with each other.

When you know that the color you wish to create can be mixed with the palette of colors, your choice then becomes quite easy. And, you then become more confident in your ability to create the color you desire.

Is the color you wish to paint an “Orange”? Then, mix the Permanent Alizarin Crimson with Cadmium Yellow Light. Is your mixture too light, compared to that of your reference? Then add either White, or Yellow, or both, to your mixture to match that color. Is your mixture too dark, compared to that of your reference? Then, add either Brown (Burnt Umber), or Ultramarine Blue, or both, to match the color of your reference.

Once you have created a color mixture, take a brush (not a palette knife) and smear a bit of your color right onto the color area of the photo that you wish to match. Protect your photo with a clear plastic sheath, and smear the paint right on it. Wipe it off when you are finished.

The choices of these colors becomes quite logical, and second-nature, once you have done it a few times, like 5 or 6. It does really NOT require a lifetime of “experience”, or “skill”. It is a simple, straightforward operation, and it can be learned!

That’s all there really is to knowing how to select, and to mix colors to match a reference.

Oh,……..and, if I were a beginner, I most definitely WOULD use a reference photo to begin my journey down the color-mixing road. It’s very difficult to “invent” the appropriate colors for, say, a field of grass, or weeds, or a tree trunk, without having something as a guide to which you can match your paint mixtures.

Design first. Color later.

Have a look at this video from Mark Carder which explains colour mixing using the colours that WFMartin recommended:

https://www.youtube.com/watch?v=NeyYXMl934g

Pinguino, you said to design first – can you elaborate more on what design means? …

With the possible exception of the “Abstract Expressionism” school of art, painters began with sketches (pencil or ink). Not merely outlines. You can find the extensive works of many famous artists online, and note that they typically began with sketched studies of what they were trying to do. The studies might be limited to a single thing, such as the expression on a face. Eventually the sketches gelled into a plan of the final composed work, which might have had values indicated in sketch before they were in paint. Final color came last, since color is usually the easiest thing to adjust if it’s not right the first time.

Design involves choosing what you will show, and choosing what you will not show. For example, many new painters seem to like green, because it’s all around in a landscape. But nature isn’t as green as you might think! Also, foliage often gets its interest from fine details that you could not render with a brush. In this case, you would have the convey foliage by masses of light and dark, and modulations of color. And, if your scene contains uninteresting elements, you will choose to eliminate them.

You can paint values then colorize them, or prepare properly-valued paint mixtures on your palette then apply them directly. The technique is up to you. I don’t have the skill to get proper values (or color) directly by mixing on the canvas; I have to first create close-enough mixes on the palette, then later correct them on the canvas.

There are exceptions; AFAIK Van Gogh apparently “thought in color” directly.

One of the Wet Canvas regulars (handle is “DCam”) often exhibits work here (oil painting forum), along with its sketch to near-engineering standards. Have a look. But that’s not necessary for everyone; it might work for you, given what you wrote above.

Many American newspapers carry a comic strip named Zits. Often, its Sunday strip begins with the artist’s preliminary sketch of one of the characters.

A design (sketch) does not need to meet engineering standards. For example, many old-school cartoons (original Bugs Bunny, Daffy Duck, etc.) were hand-drawn and intentionally distorted features and placement, for effect. Modern CGI cartoons may have technically accurate motion and perspective, but that doesn’t necessarily make them more interesting. In other words, the degree of accuracy depends on what you are trying to do.

Gosh, I made a colossal mistake in what I said, and nobody caught it.:o

First, …..If your color mix is too light, then add either Brown, or Ultramarine Blue, or both (to darken it).

If your color mix is too dark, then add either White, or Yellow, or both (to lighten it).

Sorry about making such an erroneous statement previously.