I think I have found a bug. As can bee seen in the image below, one is able to "switch off" the bid and aks price lines by selecting "None" as the color.
In MQL5, you can address These option using the following Code:
ChartSetInteger(0,CHART_COLOR_ASK,4294967295); // the last parameter "4294967295" defines the "None" color. I found this number in the exported template after setting the colors to "None"
However, this only seems to work for the ASK Price Line. Regardless which color I put for the BID Price Line it has no effect. That is where I think there is a bug in MQL5 or am I missing something?