RGB isn't even a good system to lighten or darken colors. CSS supports HSL which is certainly more intuitive. Then again, it's easier to use a good pre-processo

RGB isn't even a good system to lighten or darken colors. CSS supports HSL which is certainly more intuitive. Then again, it's easier to use a good pre-processor with color functions to darken($color, 10%) and so on (quickly, can you tell me what is 10% lighter than 2222FF off the top of your head?). Still, in the end it makes most sense to use tones from a good color palette then to mess around with hex values.