I've been using these colors for over 10 years. It started simple with just Red/White/Black, (which I still use). As time went on, I wanted to add some related brands that ultimately do very different things. (Music, Pixel Art, Sprite Sheets, Character Design and Audio Engineering to name a few.)
The principle was simple. Use the letters "RGB", and have the resulting color relate to one another. Most often use #FFFFFF and #232323.
I've used these colors for Character Design, Pixel Art, Sprite Sheets and even Music Branding. As you can see, at one point I combined the R/B in "RGB" to create a strong, saturated purple. #E1E1E1 and #4c4646 are used very rarely.