After filling them out, Sacramento County residents can either mail their ballots out to the local elections office or leave them in an official drop box - though they must be postmarked by November 3 - or drop them off at a vote center, where in-person voting will still be taking place.
But, "voters in Washington do not need to request a ballot, as ballots are automatically mailed to all registered voters at least 18 days before Election Day", said Secretary of State Kim Wyman in the statement. "These false statements will confuse Colorado voters, likely causing otherwise-eligible voters to wrongly believe that they may not participate in the upcoming election".
"There is information on this postcard that is not relevant to the voters in California and causing confusion", said Janna Haynes, a spokeswoman for Sacramento County. "This attempt at voter suppression violates the United States Constitution and federal statutes and must be stopped immediately".
The mailers include general information about mail-in voting and encourage voters to request mail-in ballots and submit them with ample time.
"In Colorado, every registered voter is sent a ballot without having to make a request and voters are urged to return ballots by mail sooner than seven days before the election", she added.
Washington is one of only five USA states that vote exclusively by mail.
The suit seeks to have the court issue an injunction prohibiting USPS from continuing to deliver any additional mailers within the state.
Many states do require advance requests for mail-in ballots, but in California, all active registered voters will sent a ballot for the 2020 election, starting October 5.
"It's my job to try to stop misinformation and any unnecessary election confusion", Griswold continued. "I will do everything in my power to stop @USPS from sending misinformation to voters".
DeJoy, a supporter of President Donald Trump and a former Republican Party fundraiser, has come under fire from Democrats for instituting cost-cutting reforms at the post office that have slowed the processing of mail.