The value of dashboards and visualizations are that they allow users to shift from serial to parallel processing. When reading a block of text you can only process the information serially by starting at the top left of the text and finishing the bottom right. Dashboards and data visualizations allow you to absorb information in parallel making it easier to absorb information quickly, identify relationships and trends.
However, the lack of serial processing requires that dashboards be effectively designed so that information can be absorbed as easily as possible. This requires that dashboard be designed for pre-attentive processing or for "the unconscious accumulation of information from the environment" (Wikipedia). Pre-attentive processing is specifically designed for parallel processing. Pre-attentive processing allowed our ancestors to continually scan the horizon to identify opportunities and threats. If well designed, a dashboard is modern-day equivalent of the horizon of the savanna, a data rich experience where it is easy to absorb the most important information, identify relationships and spot trends.
The basic principle of designing a pre-attentive dashboard that enables parallel processing is to keep element natural. Replace bright bold colors with neutral and natural hues, and pie charts, gauges and traffic lights with hue, intensity, location, orientation, line length, line width, size, shape, added marks, enclosure, and motion.