[474] How is "Possessing form, one sees forms" a liberation (vimokkha)?
Here someone attends internally, in his own person, to the blue sign (nimitta) and obtains the perception (saññā) of blue. He makes that sign well grasped, bears it well in mind, defines it well. Having made that sign well grasped, having borne it well in mind, having defined it well, he applies the mind (citta) to the blue sign externally and obtains the perception of blue. He makes that sign well grasped, bears it well in mind, defines it well. Having made that sign well grasped, having borne it well in mind, having defined it well, he cultivates it, develops it, makes much of it. It occurs to him thus: "Both this — the internal and the external — is form (rūpa)"; he is one who perceives form. Here someone attends internally, in his own person, to the yellow sign, to the red sign, to the white sign, and obtains the perception of white. He makes that sign well grasped, bears it well in mind, defines it well. Having made that sign well grasped, having borne it well in mind, having defined it well, he applies the mind to the white sign externally and obtains the perception of white. He makes that sign well grasped, bears it well in mind, defines it well. Having made that sign well grasped, having borne it well in mind, having defined it well, he cultivates it, develops it, makes much of it. It occurs to him thus: "Both this — the internal and the external — is form"; he is one who perceives form. Thus "Possessing form, one sees forms" is a liberation.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.