In MQL5, you cannot directly change the color of an indicator from within an Expert Advisor. When an EA uses built-in indicators like iMA or iRSI, it only reads their data and does not control how they appear on the chart. The color and style of an indicator can only be defined inside the indicator’s own code using properties such as #property indicator_color1 clrRed or by calling PlotIndexSetInteger(0, PLOT_LINE_COLOR, clrRed). If you need a specific color, you must edit the indicator’s source file or create a custom indicator with your preferred color settings.