成唯識論述記 3.182

3.182

述曰：心心所同所依所緣，俱依一根，緣一境故。「行相相似」，俱有似境相，隨是青等行相各別，總相似故。雖受以領納為相，想以取像為相等，一一心心所，各有青等行相，故（名為「相似」）。

The Commentary states: Mind and mental factors share the same basis (āśraya) and object (ālambana), because both rely on one faculty and cognize one object. "Their ākāras are similar": both possess a mark resembling the object; although their individual ākāras vary according to whether it is blue or the like, they are generally similar. Although vedanā has taking-in as its mark, and saṃjñā has grasping characteristics as its mark, each and every mind and mental factor has an ākāra of blue or the like, hence [they are called "similar"].