Change shield fill in ArcGIS Vector Tile Style Editor

[JoannaMerson2]

I am editing an existing basemap style and so far this tool is pretty great. However, I can't seem to change the fill color of the highway shields. Any suggestions?

[SarahHartholt]

click on edit icons and patters. Select the sprite you wan to edit and change the HEX # or click the box with the red slash through it to select a colour from the colour wheel.