It is a well-known fact that Shani Dev just like Maa Kali was dark in complexion. This is the reason his idol in every temple is black. Interestingly, his colour neither has anything to do with the immense fear surrounding his name nor on his anger that has the capacity to change one’s future.
There is a whole mythological story on how and why Shani Dev was born black –
Lord Surya’s wife Sanjana created her shadow Chayya so that Chayya could replace her and live along with Lord Surya and her children. Sanjana was upset with the radiance of Lord Surya and wanted to get rid of him as soon as possible. This is the reason why she planned everything without telling anybody.
When Sanjana left. Chhaya replaced her as Lord Surya’s wife. The two lived happily. Shani Dev was Chhaya and Lord Shani Dev’s son. According to a story, when Shani was in the womb of Chhaya, a Shiv bhaktini. she was absorbed in a great penance.
She prayed so intensely that she did not care for food or water. She stood tall in the blazing sun without having anything. It was because of this penance by pregnant Chayya for Lord Shiva in the intense heat turned the complexion of Shani Dev completely black.
Seeing the dark-complexioned baby, Lord Surya was shocked. His complexion made Lord Surya doubt his wife Chayya. He even insulted her by saying that the child born is not his son. While the colour made his look strange in the eye of the Lord, it did bring in many powers. It was because of this penance by his mother that Lord Shani was born powerful. He had immense ‘shakti’ from the day he was born.
So, when Lord Surya started insulting his mother Chayya, Shani saw his father with a strange gaze because of which Surya’s body turned black. Next, the horses of his chariot stopped moving and he became total helpless. Worried about the situation, Lord Surya called Lord Shiva for help. Knowing everything, he explained Surya the main reason of Shani’s blackness. After all, Chayya was meditating in the name of Lord Shiva.
Post hearing the entire story, Lord Surya not only apologized in front of Chayya but also accepted his fault. Next, he regained back his radiant look and soon even the horses of his chariot started moving. The family reunited happily without having any further qualms.