Using colormaps
Color coding the data can have a great impact on how your visualizations are perceived by the viewer, as they come with assumptions about color and what that color represents.
Being explicit, if the color is used to add additional information to the data, it is always good. To know when and how to use color in your visualizations is even better.
Getting ready
If your data is not naturally color coded (such as earth/terrain altitudes or an object's temperature), it's better not to make any artificial mappings to natural coloring. We want to understand the data appropriately and so make a choice of color to help the reader decode data easily. We don't want readers constantly trying to suppress learned mapping of color for temperatures if we are representing financial data that has no connection with Kelvins or Celsius.
If possible, avoid usual red/green associations if there is no strong correlation in the data to associate them with those colors.
To help you pick the right color...
