Sequential schemes
Variations in lightness make these schemes ideal for mapping orderable or numeric data that progress from low to high using colors that range from light to dark (or vice versa).Think about basemap contrast. For a light basemap, darker shades should denote high values; for dark basemaps, this should be reversed.
Diverging schemes
Highlight values above and below a mid-point in quantitative data with these schemes. The middle color is assigned to the critical value with two sequential type palettes at either end assigned to values above or below. Diverging schemes are ideal for denoting a range of positive or negative values, such as change over time.
Beware the red-green color ramp! 8% of men and 0.5% of women suffer from red-green color blindness, and may struggle to interpret this color scheme.