Rank Trend view displays a color-coded trend of rankings for a set of keywords over a specified date range. The colors range from dark blue at the highest ranks to dark orange at the lowest. The rank trend for a keyword can be seen in a few different features including Dashboards, Rank Intelligence and Keyword Detail by clicking the Trended View toggle above the results list. First set the date range for the time period over which you want to see a trend.

Rank Intelligence - Trended View Learn More

Keyword Detail Overview - Rank Trend