I agree and the grain/transparency effect specifically looks like the gradients made using a (physical) airbrush that show up a lot in the Memphis style.

1. https://www.etsy.com/listing/1402316103/memphis-style-postmo...

(Scroll down about halfway for the next one)

2. https://www.chairish.com/product/6986561/vintage-1980s-memph...

3. https://glowgeometric.com/products/1980s-hollis-fingold-memp...