Though note, it’s not really ideal for making gradients, since its “sequential” schemes only go up to 9 distinct categories, and its “diverging” schemes only go up to 11 distinct categories. If you took the suggested colors and made them equally spaced control points in a photoshop/CSS/etc. gradient, you’d get a reasonable outcome.
Also for gradients, I wrote a pretty simple colormap editor here: http://colormap.org/. This maybe gives too much freedom, since it doesn't enforce any best practices as far as colorblindness is concerned. But if you make sure the brightness (the gray line) is monotonic, it's a step in the right direction.
Though note, it’s not really ideal for making gradients, since its “sequential” schemes only go up to 9 distinct categories, and its “diverging” schemes only go up to 11 distinct categories. If you took the suggested colors and made them equally spaced control points in a photoshop/CSS/etc. gradient, you’d get a reasonable outcome.