visualize data using ggplot in R based on the following awesome tutorials:

http://www.cookbook-r.com/Graphs/Bar_and_line_graphs_(ggplot2)/ @阿力木大

https://ggplot2.tidyverse.org/ @Haoyang

http://colorsupplyyy.com/app/ @旺仔小牛奶

http://colorbrewer2.org/ provide really thorough combination of colors that are readily adoptable.