It is unfortunately not possible to specify the colors within the formula language.
To change the colors, you will need to do the following :
Apply the indicator on your chart, you should see 2 red lines, right click on the first one and select properties. Change the color and click on ok. Right click on the second red line, go to properties and change the color and click on ok.
So that you do not have to do this every time I would recommend saving this as a template, see your default template.
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