Forney Industries, Inc. sells tools and accessories. They use a multi-color gradient on their product packaging. They applied for a trademark for their color gradient on the basis of inherent distinctiveness. The USPTO rejected that argument. Forney appealed to the Court of Appeals for the Federal Circuit, and the Federal Circuit overturned the USPTO (In re Fourney, Case No. 2019-1073 (Fed. Cir. April 8, 2020), opinion hosted on Mega.nz).
Interpreting US Supreme Court cases, the Federal Circuit found that color trademarks for product design are not inherently distinctive and thus require proof of acquired distinctiveness). The Federal Circuit also found -- in Forney's favor -- that color trademarks for product packaging can be inherently distinctive.
Until the Supreme Court takes this issue up, I would expect other applicants to try to register the colors on their product packaging.
Image from Fed. Cir. opinion at page 2.