Solved
How to add back ground colour to subject line in gmail preview
I have received some emails from glassesusa where on viewing mt gmail in box they have a subtitle with a coloured background shows as below;
stephen.trumbleAnswer
Klaviyo Alum
January 30, 2023
Hey
Thanks for asking about this! While Klaviyo not not have a native option for this, I did find an article from email on Acid on How to Display Images and Offer Information in the Gmail Promotions Tab [Free Tool]. You could create a full customized option for this.
Hope this helps!
-Stephen