Yes, your deposits are covered by the FSCS (subject to eligibility).
Please note: Cash you deposit into UK banks or building societies (that are authorised by the Prudential Regulation Authority) are protected by the Financial Services Compensation Scheme ("FSCS"). The FSCS deposit protection limit is £120,000 per authorised firm.
Marygold Easy Access Saving Accounts are provided by Griffin Bank Ltd. This means deposits held in these accounts, together with any other Griffin-provided accounts you might have, are considered to be one authorised firm. Deposits in excess of £120,000 held in any account provided by Griffin Bank Ltd would not be eligible for FSCS protection.
For full details the best thing to do is head to Griffin's deposit protection page, where you can find detailed information about what is and is not covered, as well other links to the FSCS, FCA and PRU rulebook.