The Color Wheel
From Scribus Documentation Project
Using the Color Wheel in Scribus brings you back to design school and it certainly will help you to refresh your knowledge about the usage of color in your layout. The tool is placed in Extras > Color Wheel and it opens in a new window:
On the left you see the Color Wheel, on the right a live display of your actions, and the table below shows your instant results in plain numbers – the values for CMYK (Cyan, Magenta, Yellow, Black). The traditional RYB  color model, with red and green, blue and orange, and yellow and purple as complementary pairs, is a historical set of subtractive primary colors. This model is mainly in use by visual artists – in digital media it has been replaced by HSV and HSL within the RGB color model.
This does not mean that RYB has lost his significance as a design reference. Scribus, however, uses the RGB space and implements six different methods to specify color schemes. Below the color wheel you can select from a drop down menu:
- Analogous 
- Split Complementary 
- Tetradic (Double Complementary) 
A monochromatic color scheme is based on a single color with variations of lightness/shades. When you move your mouse over the color wheel the red dot in the “orbit” indicates your base color. The Scribus color wheel does not include variations of lightness at this point. Thus, it does not matter if you move around inside the wheel. A monochromatic color scheme allows paler or more saturated tints of the base color, also called the main color. While moving around, you will notice changing CMYK values for the base color, a monochromatic dark and monochromatic light in steps of 50% lightness. You can use other tints, shades, and tones of the key color to enhance the scheme.
Analogous colors are a palette of color combinations that are neighbors on the color wheel. If you stay in the color wheel below and angle of 60 degrees the tool generates harmonious combinations. From 60 degrees on it begins to generate complementary pairs. First you will notice complementary pairs according to the RYB space and at 90 degrees you will find a full complementary pair within the RGB color space. While moving around you will notice changing CMYK values for a base color, the 1st analogous, and the 2nd analogous color. Avoid combining warm and cold colors.
Complementary colors correspond via opposite sides in the color wheel, in an angle of 180 degrees. They can be generated in any color value, even in different shades. Move around with the mouse pointer and observe how the contrast changes to more or less vivid combinations. When you move the pointer to a clear yellow, for instance, the opposite blue is dark and may need an adjustment by increasing its lightness to achieve a more vivid and at the same time a more harmonious combination.
The split complementary schemes offers an alternative to the tension of the complementary scheme. Use the angle option to specify the range. At 0 and at 90 degrees, you will get a complementary pair, at 90 degrees you will also have a base color. Between 0 and 90 degrees you generate two complimentary pairs that go through the analogous color dimensions. In practice you may work with the Base Color and the 3rd and 4th split to create a soft complementary pair. If you use a base color and the 1st and 2nd split you will have an analogous scheme. Avoid dull warm colors – instead use a single warm color paired with two cold colors or vice versa.
Triadic Colors schemes are highly energetic color schemes based on three colors separated by 120 degrees on the color wheel. The primary (red, blue, and yellow) and secondary (purple, orange, green) colors are examples of triadic colors. This scheme is popular among designers and artists because it offers strong visual contrast while retaining balance, and color richness. This scheme has less contrast than a complementary scheme and will appear to be harmonious and balanced. It may be a good idea to choose one color as dominant and subdue the remaining by changing shade and saturation or by balancing color usage, distribution and accents in a layout.
Tetradic (Double Complementary)
Of all color schemes the tetradic (double complementary) is the richest. It employs four colors arranged into two complementary pairs. As you will see with the Scribus color wheel, the scheme is hard to harmonize because all four colors appear in more or less equal values. It may look unbalanced, conflicted, and you should choose one of the four colors to be dominant and subdue others. Although the color wheel suggests it, avoid using those colors in equal amounts. Think in terms of dominating, secondary and accent colors.
The recognition of color combinations will be different for each human being. Aside from personal taste, customs and cultural backgrounds, not one human's eyes will see exactly the same colors. While the differences may be minimal in many, if not most cases, some people's color reception capabilities differ significantly to those of the majority. This phenomenon is referred to as “color blindness”.
Designers may need to test their color combinations for people who suffer from color blindness, as, in extreme cases, they won't be able to tell the difference between some colors. The Color Wheel provides an option to emulate some widespread forms of color blindness, a feature that, despite its usefulness, is rarely found in most graphics applications. It enables users to detect issues with certain color combinations before a document is published. To the best knowledge of the Scribus team, Scribus is the only DTP application with this as a built-in feature.
In the upper right corner you find a menu for “Vision Defect”. Choose “Full Color Blindness”, and you will see only gray values. There are also options to emulate protanopia, deuteranopia, tritanopia.
 Allows additional variations in angles from 0 to 90 degrees.