Best shown using a singleordichromaticcolorforlinesincreasingthicknesscanillustratelargervaluesandincreasingmarkersizeistypicallyusedforpoints
Avoid vibrating color patterns such as thick alternating white and black lines because they are tiring and unpleasant to look at they are called moiré patterns however thinning the lines increasing the separation and making the white background transparent creates an effective symbol to show the extent of urban area
Emphasize important information by using dark and bold colors large sizes or high contrast with surrounding map elements deemphasize less important information using pale colors turning black to gray or using transparency
Examples
In we see the population density and highways of the san Francisco area in a rainbow color ramp was used but the sense of increase is not obvious the lower density counties are dramatized in dark red drawing inappropriate attention to them the preponderance of mixed bold colors is also tiring to look at this map is aesthetically poor and difficult to interpret
In the rainbow color ramp is replaced set of browns making it obvious which counties have high populations the color balance seems far more restful and pleasant the highways are shown in a contrasting green for good legibility and the urban highways which are shorter and more difficult to spot have been put in bright green to enhance their visibility the major interstates are shown as thick liens and the highways as thin lines delineating them relative to the roads the final map is clearer more attractive and less cluttered than the original