"The Golden Saguaro". There are only 9 documented full Golden Saguaros in existence and this is the largest. Thanks to Joe Orman of the Crested Saguaro Society for giving me the opportunity to photograph this rarest of saguaros. "Golden Saguaros" have abnormal coloration ranging from a pale yellow to a bright golden color; this coloration can be on all or just part of the saguaro. Cactuses with non-uniform coloration are known as variegated cactuses. Variegation is due to a rare mutation wherein the plant's meristematic tissue loses the ability to produce cholorplasts, causing a lack of chlorophyll in the epidermis.
https://www.crestedsaguarosociety.org/.../golden/golden.php