There isn't a common weed or bug known as "red jacket" that lives in grass. It's possible there's a local name for a specific species in your area, but it's not a widely recognized term.

Could you give me more information?

* Location: Where are you located? This could help narrow down possibilities.

* Description: What does the "red jacket" look like? Is it a plant or an insect?

* What makes it stand out? Is it the color, shape, or size that makes it unique?

With a more detailed description, I might be able to help you identify it.