The same practice exists in the Gelug and Phabongkha Rinpoche says its permissible to visualize the 35 Buddhas as being in the aspect of the Dhyani Buddhas. The first seven as Akshobhya, then Vairochana, Ratnasambhava, Amitabha, and Amoghasiddi. The two exceptions are Shakyamuni and King of Powerful Nagas (Geyaraja). Shakyamuni appears same as always and King of Powerful Nagas is white above the neck but blue below the neck. Also he makes the mudra of subduing nagas (not sure what this looks like).
Paraphrased from Liberation in the Palm of Your Hand Pg. 221-222
Also, it's not the case that there will be no benefit if you visualize some Buddhas slightly wrong. More importantly:
“I must stress here that visualize does not mean you should try to paint a picture of the refuge tree in your mind; that would be impossible. Visualization is very like thinking about the person who is closest to you in this life-your mother, for example. Try imagining her standing in front of you right now. As you do so, I’m quite sure you are not thinking about the exact shape of her ear. Or whether or not her toes curl. Or how many moles she has on her back. In fact, that kind of detail has probably never even occurred to you. At the same time, I am equally sure that you have created a strong sense of your mother in your mind and that you are completely confident it really is her. This is how you should visualize the objects of refuge, and the confidence you feel in your visualization is of utmost importance.”
-Not for Happiness pg. 103-104
Equanimity is the ground. Love is the moisture. Compassion is the seed. Bodhicitta is the result.
-Paraphrase of Khensur Rinpoche Lobsang Tsephel citing the Guhyasamaja Tantra
"All memories and thoughts are the union of emptiness and knowing, the Mind.
Without attachment, self-liberating, like a snake in a knot.
Through the qualities of meditating in that way,
Mental obscurations are purified and the dharmakaya is attained."
-Ra Lotsawa, All-pervading Melodious Drumbeats