There is a CKEditor plugin called Color Button that can be used to add buttons to CKEditor instances to change font colors and background colors.

If you have this plugin installed, you may have noticed that the default colors available (see this post's featured image above) seem like a strange assortment of defaults, with many colors not existing at all in any shade. Which is strange, since the featured screenshots in the Color Button plugin's download page, such as this one [mirror] seem to show a fairly logical/normal assortment of colors. Perhaps some shit has somehow been fucked up in my installation/setup.

Anyway, the point is, you can set custom colors. Go to the config.js file for CKEditor and add these lines of code for the set of colors shown on the right side of the featured image for this post.

// Enable the plugin
config.extraPlugins = 'colorbutton';

// Six Shades of All Colors.
// Code for changing the default color set for CKEditor's Color Button plugin.
// Color Button has six columns, so six shades/tints per color lines up cleanly.
// https://www.color-hex.com/color/ff0000
// https://www.256kilobytes.com/content/show/11413/table-11-shades-and-11-tints-of-all-colors-in-hexadecimal-form
config.colorButton_enableAutomatic = true;
config.colorButton_colors = 
"ff0000,e50000,b20000,ff7f7f,ffb2b2,ffe5e5," + // Red   
"ff00ff,e500e5,b200b2,ff7fff,ffb2ff,ffe5ff," + // Magenta    
"800080,730073,590059,bf7fbf,d8b2d8,f2e5f2," + // Purple   
"ee82ee,d675d6,a65ba6,f6c0f6,f9d9f9,fdf2fd," + // Violet   
"0000ff,0000e5,0000b2,7f7fff,b2b2ff,e5e5ff," + // Blue   
"00ffff,00e5e5,00b2b2,7fffff,b2ffff,e5ffff," + // Cyan   
"008000,007300,005900,7fbf7f,b2d8b2,e5f2e5," + // Green   
"7fff00,72e500,58b200,bfff7f,d8ffb2,f2ffe5," + // Chartreuse   
"ffff00,e5e500,b2b200,ffff7f,ffffb2,ffffe5," + // Yellow   
"ffa500,e59400,b27300,ffd27f,ffe4b2,fff6e5," + // Amber   
"ffa500,e59400,b27300,ffd27f,ffe4b2,fff6e5," + // Orange   
"ff4500,e53e00,b23000,ffa27f,ffc7b2,ffece5," + // Orangered    
"a52a2a,942525,731d1d,d29494,e4bfbf,f6e9e9," + // Brown   
"000000,333333,666666,999999,cccccc,ffffff"   // Black/White/Grey

See Also:

• https://www.color-hex.com/color/ff0000
• https://www.256kilobytes.com/content/show/11413/table-11-shades-and-11-tints-of-all-colors-in-hexadecimal-form

Re: This is not live on 256 Kilobytes currently, but will be in the next patch. 

Sir, I can do you a nice SEO.