How many centers can be colored in
None and all nine — both cases exist, but they’re rare. Most people have three to six colored in. More colored in isn’t “a better chart”: it means more consistency and less flexibility. Fewer isn’t worse: it means sensitivity and, over time, real wisdom in those areas where the person has seen every shade.
A person without a single colored-in center is called a Reflector, and there are roughly one in a hundred of them. They reflect the place they’re in: in good company they blossom, in bad company they fade — and it really is the company.
Why there are nine centers but seven chakras
The system grew out of the Indian chakra tradition, but in Human Design there are nine, not seven: the throat and solar plexus nodes are split into several independent centers. So there’s no point looking for a direct match between the “heart chakra” and the Heart (Will) center — the name matches, not the content.
Where to start reading
First look at which of your centers are open, not which are colored in. The colored-in ones work on their own anyway — they don’t need attention. But the open ones explain the most frustrating things: why next to one person you act decisively and next to another you get lost; why after a noisy gathering you take two days to recover; why you set out to prove things nobody asked you to prove.
And a caveat right away: an open center isn’t a defect or a diagnosis. It’s the place where you’re more sensitive than others. There’s exactly one way to spoil it: to take what belongs to others for your own and live by it for years.