code: public void setTrackColor(ColorStateList stateList) {
          mTrackStateList = stateList;
          mTrackColor = mTrackStateList.getDefaultColor();
          if (mAlpha < 255) {
              mCurTrackColor = Ui.modulateColorAlpha(mTrackColor, mAlpha);
          } else {
              mCurTrackColor = mTrackColor;
          }
      }
docs: Set the Track ColorStateList
  
  @param stateList ColorStateList