The truth is that there are no rigid rules. However, for a huge open concept space, I usually recommend painting 2 main colors from the same paint card (a lighter color, and another slightly darker but still light shade). This will help with spaces that don't have as much natural light as others but still look consistent. To those, I usually add 2-3 accents colors, which could be finishes such as wood tones, blacks, or more vibrant colors too.