We had some reports that customers who wanted to see their surface in Realistic view were always seeing these triangle lines and that they were always gray no matter what color is set in the style. The keyword here is STYLE. These settings are part of the visual Style settings and not objects style. To access these settings please see the steps below.
2. Select Realistic style and under Edge Settings set Edge Mode to None if you do not want these triangle lines to show
3. If you want them to show with color closer to the Render Materials set color as you wish
4. OK and then select your surface and show it in Object Viewer (right-click)
5. It should show up without these triangle lines.