Methyltransferase that mediates the O-methylation of 1-hydroxy carotenoids. Converts hydroxyneurosporene to methoxyneurosporene or demethylspheroidene to spheroidene. Also able to produce spirilloxanthin (By similarity). demethylspheroidene + S-adenosyl-L-methionine = H(+) + S-adenosyl-L-homocysteine + spheroidene Carotenoid biosynthesis; spheroidene biosynthesis. Belongs to the class I-like SAM-binding methyltransferase superfamily. Cation-independent O-methyltransferase family.