The DRAW_COLOR_HISTOGRAM2 drawing style is used to plot color histograms using two indicator buffers, the colors are specified in the color buffer.
For each bar it plots a section between the Open and Close prices. Three indicator buffers are used: the first contains the High values of the bar, the second contains the Low prices of the bar, the third buffer contains the color indexes. The colors, width and line style are changed randomly after N ticks. The initial properties of the plot1 graphic plot are defined using the #property preprocessor directive, further these properties changed randomly (see OnCalculate() function).
See also The Drawing Styles in MQL5