colormap: [ '#000FFF', '#68E8FB', '#00FF00', '#FFF000', '#FF0000', ]
colormap: function(x) { return {r: 255*x, g: 0, b: 0, a: (1+x)/2}; }
colormap: { hue: { start: 360, end: -360, saturation: 50, brightness: 100, colorStops: 8, } }
colormap: [ '#000000', '#6A0DAD', '#FFFFFF', ]