Anguttaranikaya 8.2.2.5: 5. Abhibhāyatanasuttavaṇṇanā

In the fifth [discourse], 'bases of mastery' (abhibhāyatanāni) means grounds of mastery. What do they master? Both adverse qualities and objects. For by being their opposite, they master adverse qualities; and through the excellence of the individual's knowledge, they master the objects. In the phrases beginning with 'perceiving form internally' (ajjhattaṃ rūpasaññī), one is called 'perceiving form internally' through preliminary work on an internal form. For making the blue preliminary work internally, one makes it on the hair, or on bile, or on the pupils of the eyes. Making the yellow preliminary work, one makes it on fat, or on the outer skin, or on the palms of the hands and the soles of the feet, or on the yellow parts of the eyes. Making the red preliminary work, one makes it on flesh, or on blood, or on the tongue, or on the red parts of the eyes. Making the white preliminary work, one makes it on the bones, or on the teeth, or on the nails, or on the white parts of the eyes. But that is not pure blue, pure yellow, pure red, or pure white; it is completely unpurified.

'One sees forms externally' (eko bahiddhā rūpāni passati): for one whose preliminary work has arisen internally in this manner, but the sign [arises] externally, he is said to be 'perceiving form internally, one sees forms externally' by virtue of the internal preliminary work and the external absorption. 'Limited' (parittāni) means unexpanded. 'Beautiful and ugly' (suvaṇṇadubbaṇṇāni) means whether they are beautiful or ugly, it should be understood that this base of mastery is spoken of purely with respect to what is limited. 'Having mastered them' (tāni abhibhuyya): just as a man with a hearty appetite, having received a mere spoonful of food, pushes it together and makes a single mouthful, thinking, 'What is there to eat here?', even so an individual of superior knowledge, with clear knowledge, thinking, 'What is there to attain in this limited object? This is no burden for me,' masters those forms and attains [absorption]; the meaning is that right with the arising of the sign he brings about absorption. By 'I know, I see' (jānāmi passāmi), his advertence is spoken of. And that belongs to one who has emerged from the attainment, not inside the attainment. 'Is so perceiving' (evaṃsaññī hoti): he is one who is so perceiving both by perception of advertence and by perception of jhāna. For his perception of mastery exists even inside the attainment, but the perception of advertence belongs only to one who has emerged from the attainment.

'Immeasurable' (appamāṇāni) means with an expanded measure, meaning large. 'Having mastered' (abhibhuyya): here, too, just as a gluttonous man, having received an enlarged portion of food, does not see it as large, thinking, 'Let there be another, let there be another, what will this do for me?', even so an individual of superior knowledge, with clear knowledge, thinking, 'What is there to attain here? This is not immeasurable; there is no burden for me in producing one-pointedness of mind,' masters it and attains [absorption]; the meaning is that right with the arising of the sign he brings about absorption.

'Perceiving formlessness internally' (ajjhattaṃ arūpasaññī) means devoid of the perception of preliminary work on internal form, either due to non-attainment or due to lack of need.

'One sees forms externally' (eko bahiddhā rūpāni passati): for one whose preliminary work and sign have both arisen externally, he is said to be 'perceiving formlessness internally, one sees forms externally' by virtue of the external preliminary work and absorption. The rest here and in the fourth base of mastery should be understood just in the manner stated. Among these four, however, the limited is presented for one whose temperament is speculative, the immeasurable for one whose temperament is deluded, the beautiful for one whose temperament is hateful, and the ugly for one whose temperament is greedy. For these are suitable for them. And their suitability is stated in the Visuddhimagga in the Exposition of Temperament.

In the fifth base of mastery and the rest, "blue" is spoken comprehensively. "Blue in color" is by way of color. "Showing blue" is by way of appearance. It is said that they appear as an unbroken expanse of blue, without visible gaps and with unmixed color. "Having a blue luster" is spoken by way of radiance; the meaning is: having a blue glow, endowed with blue radiance. By this, their supreme purity is shown, for these bases of mastery are spoken of entirely by way of pure colors. Herein, making the kasiṇa, the preparatory work, the procedure for absorption, and all the rest—beginning with "one learning the blue kasiṇa takes the sign in blue, whether in flowers, cloth, or a colored element"—has already been explained in detail in the Visuddhimagga.