What's it called??? Sewing Machines Parts and Sales in Los Angeles

I am looking for a pattern but I don’t know what the thing I want to make is called which makes searching for a pattern exceedingly difficult.

I want to make a thing that goes over a white dress. I would make it out of sheer material so the dress itself shows through but adds color over top.

I know it’s a thing but I can’t figure out what it’s called.

If you have any patterns to suggest that’d be appreciated too!