Quite often, if you do not serialize your Brush parameters in your NinjaTrader strategy or indicator you will be fine but only until you try saving your presets. When a preset is saved all parameters are actually serialized into a string on the backend and if you have not handled the Brush parameter properly in your code then you will get a problem, you won't be able to save parameters and NinjaTrader might also crash. Below is how to properly handle this situation:
[XmlIgnore]
[NinjaScriptProperty]
[Display(Order = 20, Name = "Dıamond Color", GroupName = "Parameters")]
public System.Windows.Media.Brush DıamondColor { get; set; }
[Browsable(false)]
public string MyBrushSerialize
{
get { return Serialize.BrushToString(DıamondColor); }
set { DıamondColor = Serialize.StringToBrush(value); }
}