code: public void setThumbColor(ColorStateList stateList) {
          mThumbStateList = stateList;
          mThumbColor = mThumbStateList.getDefaultColor();
  
          if (mAlpha < 255) {
              mCurThumbColor = Ui.modulateColorAlpha(mThumbColor, mAlpha);
          } else {
              mCurThumbColor = mThumbColor;
          }
      }
docs: Set the Thumb ColorStateList
  
  @param stateList ColorStateList