arcgis Desktop 10.2.2 ArcObject change IMultiLayerLineSymbol color

[testtest7]

I am trying to change symbol color through ArcObject , but only part of symbol can be change(fig 1.). The setting which is inside in nested symbol setting page (fig2). I use the follow the code below to change the first layer's color.Does any one know how to recursive loop all symbol's porperties? Thanks

//Code

  _MultiLayerLineSymbol = _Symbol as IMultiLayerLineSymbol;

                 _LayerColorLock = _MultiLayerLineSymbol as ILayerColorLock;

                 for (int i = 0; i < _MultiLayerLineSymbol.LayerCount; i++)

                 {

                     _LayerColorLock.LayerColorLock = false;

                 }

                 _MultiLayerLineSymbol.Color = _Color;

(fig.1)

(fig. 2)