俱舍論記 28.37

28.37

「此因不成許有色故」者，大眾部、化地部等出過。皆無色故立無色名，此因不成，我許彼界亦有色故。

As for "This reason is unestablished, because it is admitted that form exists": the Mahāsāṃghikas, Mahīśāsakas, and others point out a flaw. As for 'they are given the name formless because they all lack form', this reason is unestablished, because we admit that form also exists in that realm.