Scripture says different things about this topic. For example, Laghu-bhagavatamrta says, "In Satya yuga the incarnation is said to be white in color and named Hari. In the Treta, Dvapara, and Kali yugas the incarnations are red, blue (syama), and black (krsna), respectively."
In this verse Sri Rupa Goswami seems to acknowledge that the Lord appears in every Kali yuga and that the yuga avatara of Kali yuga is black in color. However, Sri Jiva Goswami writes in his Sarva-samvadini, "The Godhead, Lord Hari, does not personally appear in the Kali yuga. Because he only appears in the Satya, Treta, and Dvapara yugas, and not in the Kali yuga, the scriptures call him Triyuga (he who appears in three yugas). Similarly, one of the names of Visnu mentioned in the Visnu-sahasra-nama is Triyuga, indicating that there is no yuga avatara in Kali yuga.
However, in Bhagavad-gita Sri Krsna says that he descends in every yuga to establish dharma, sambhavami yuge yuge, indicating the function of the yuga avatara.
Srimad Bhagavatam 7.9.38 acknowledges that the Lord is Triyuga but speaks of a covert avatara in Kali yuga, channa avatara. Srimad Bhagavatam 11.5.35 mentions either a black or golden avatara with emphasis on the idea that he is golden. In this verse the word tvisakrnsa, which is used to describe the Kali yuga avatara, can mean either black or golden, although our Gaudiya acaryas have rendered it golden. In Srimad Bhagavatam 10.8.13, the word pita (yellow) is used in the past tense indicating that in previous Kali yugas the yuga avatara was golden. None of these Bhagavatam verses give any indication that the Kali yuga avatara it speaks of does not appear in every Kali yuga.
Locana dasa writes in his Caitanya Mangala, "Some people say Lord Gaura is a yuga avatara. In truth he is the origin of all avataras. In other Kali yugas, the avatara is Lord Narayana. That avatara has a name of two syllables. That name is Krsna. The scriptures say that avatara has a complexion like a parrot's wing (yellow). Some commentators also explain that his color is dark like a sapphire."
According to Caitanya-caritamrta, Sri Krsna appeared as Sri Caitanya Mahaprabhu at a time that corresponded with the time for the descent of the Kali yuga avatara and thus he performed the function of the yuga avatara while simultaneously fulfilling his own purpose. He combined the yuga dharma with the distribution of prema. Some devotees saw him as Narayana (Gaura-Narayana), and they worshiped him accordingly, as the husband of Visnupriya and not with a view to attain Vraja prema. They worshipped him to attain love for him in dasya bhakti. This sadhana has a sadhya in which Gaura-Narayana is the object of love. Thus Gaura-Narayana is eternal, and aside from the conflicting scriptural citations above, he seems like the most suitable person to perform the function of the yuga avatara in Kali yuga.
Therefore, some acaryas have concluded that he is the yuga avatara of every Kali yuga.
The conclusion to draw from all of this is that the yuga avatara of Kali yuga is very mysterious.
Mahanidhi Swami explica:
"Em toda Kali Yuga, o Senhor Caitanya aparece para propagar o Yuga Dharma do Hari-Nama-Sankirtana.
Esta função religiosa é executada meramente por um Amsa-Avatar do Senhor.
Um Kalpa é um dia de Brahma, e um dia de Brahma consiste em mil ciclos de quatro Yugas, ou eras:mil Satya Yugas, mil Treta Yugas, mil Dvapara Yugas e mil Kali Yugas.
Somente uma vez no dia de Brahma uma manifestação plena de Svayam Bhagavam Sri Krsna e Svayam Bhagavam Sri Caitanya aparecem neste mundo material.
Porque a Suprema Personalidade de Deus Sri Krsna e Sri Krsna Caitanya aparecem?
yuga-dharma-pravartana-haya amsa haite
ama vina anye nare vraja-prema dite
"Minhas (Amsas) porções plenárias podem estabelecer os princípios da religião para cada era.Mas ninguém além de Mim, pode dar Vraja Prema, o tipo de serviço amoroso dos residentes de Vraja." (Cc. Adi 3.26)
Quando o Senhor Krsna aparece em Kali Yuga somente para propagar o Yuga Dharma, Ele é conhecido como Gaura Narayana.
Nesta forma, o Senhor Caitanya como Gaura Narayana, não distribui Vraja Prema ou Manjari Bhava.
Portanto, a Kali Yuga na qual estamos é muito especial, porque Svayam Bhagavam Sri Krsna Caitanya Mahaprabhu, não somente propaga o Yuga Dharma como também mostra o padrão mais elevado de serviço devocional (Manjari Bhava), o que não acontece em outras Kali Yugas.
Nós somos muito afortunados em nascermos especificamente nesta Kali Yuga, aonde Svayam Bhagavam Sri Krsna uniu-se com a compleição corpórea (Dyuti) e sentimento (Bhava) de Srimati Radharani para aparecer na Sua forma mais misericordiosa como Rasaraja Mahabhava Sri Gaurasundara.
Diferente dos muitos Senhores Caitanya que apareceram em Kali Yugas prévias, Mahaprabhu está livremente dando o mais raro presente que se pode obter, Radha Krsna Prema-Bhakti.
Que nós possamos realizar nossa boa fortuna por vivermos um pouco após do mais misericordioso Avatar Dourado.Sinceramente rendamo-nos a Ele.
E puramente cantemos o Yugala Mantra para obter Vraja Prema:
Hare Krsna Hare Krsna Krsna Krsna Hare Hare
Hare Rama Hare Rama Rama Rama Hare Hare
http://vedabase.net/sb/10/8/13/en1
http://vedabase.net/cc/adi/3/37/en
Lord Visnu is sometimes called tri-yuga because He appears in three yugas - Satya, Treta and Dvapara, but in Kali-yuga He does not appear. However, Srimad-Bhagavatam also describes the prayers of Prahlada Maharaja, which explain that the Lord sometimes appears in a concealed form in the age of Kali, garbed as a devotee. Lord Caitanya is that devotee. In Satya-yuga He is white (sukla), and Treta-yuga He is red (rakta), in Dvapara-yuga he is dark blue (syama), and in Kali-yuga he is sometimes black (krsna), and sometimes yellow (pita), like Caitanya Mahaprabhu.
In the Satya yuga a white avatar appeared to Kardama muni to establish meditation as the process for self-realization.
In the Treta yuga a red avatar appeared to Brahma to establish fire sacrifice as the process for self-realization.
In the Dvapara yuga a dark avatar (Krishna) appeared as the son of Devaki to establish temple worship as the process for self-realization.
In the Kali yuga a Yellow avatar appeared (Chaitanya Mahaprabhu) as the son of Sachi Mata to establish the chanting of the holy names (nama-sankirtana) as the process for self-realization
Yuga-Avataras
Avataras who in four different yugas (at their junctures) appear to propound the appropriate method of self-realization for the era in question:
- Rama (end of Treta beginning of Dvapara),
- Krishna (end of Dvapara beginning of Kali),
- Kalki (end of Kali, beginning of Satya).
- In Satya He is a celibate in a four-armed form preceding Treta yuga with matted hair, dressed in tree bark and a black deer skin to teach meditation. With different names as to the nature of dedication/devotion He is called Hamsa, Suparna, Vaikunthha, Dharma, Yoges'vara, Amala, Isvara, Purusha, Avyakta and Paramatma (see explanation in (S.B. 11.5: 21-23).
The four yuga-avataras are: (1) sukla (white) in Satya-yuga (S.B. 11.5: 21), (2) rakta (red) in Treta-yuga (S.B. 11.5: 24), (3) syama (dark-blue) in Dvâpara-yuga (S.B. 11.5: 27) and (4) generally krishna (black) but in special circumstances pîta (yellowl) like Caitanya Mahaprabhu in Kali-yuga (S.B. 11.5: 32 and S.B. 10.8: 13).
http://krishnascience.com/Vaisnava%20Library/Practical%20application/Four%20Yugas.htm
Haribol !!!