You can try Microsofts resolution
If the document contains lots of fields, and your Word preferences are set to highlight fields as “Always”, those fields in the document will show with
a grey highlight.
The option can be changed from the below location:
Word>Preferences>View>Field shading: “Always”
If the above does not help, follow the steps below:
1. Select the text, Go to Format > Borders & Shading. On the Shading Page, select None.
2. Select the text then click the right edge of the Highlighter tool on the Formatting Toolbar & choose None.