matlpot的color参数可以是十六进制，也可以是颜色描述的字符串。

下面是字符串描述的颜色表。为了颜色间要有区分度。同时要求颜色比较明显，特意选择一些比较有代表性的颜色，以供使用（颜色由于个人需要，除去了红色和绿色）。

colors = ["rosybrown","indianred",
         "darkred", "tomato","sienna","peru",
         "darkorange", "darkgoldenrod","olive","gold","yellowgreen",
         "darkslategray","blue","cadetblue","dodgerblue",
         "royalblue","darkslateblue","indigo", "violet",
         "m","fuchsia","deeppink","crimson"
    ]