Tile Grout Color

[hookthem]

Hi All, new Home Designer Pro user here. I'm having a hard time setting the grout color for a tiled backsplash. Here's what I've done so far:

1. Copied the "White Tile" material to my User Catalog
2. Opened the material's "Define Material" dialogue
3. In "General", I changed the Material to pure white and the pattern lines to gray
4. In "Texture" I checked the "Blend Material Color With Texture" option to make the tiles pure white

Even though the material and pattern look correct in the "General" pane, the gray grout lines do not seem to appear on the backsplash. Please see the attached screenshots.

What am I doing wrong here?

Thanks in advance!