Then when the heaven is rent asunder, and it becomes rosy or

﴿فَإِذَا ٱنشَقَّتِ ٱلسَّمَآءُ فَكَانَتۡ وَرۡدَةٗ كَٱلدِّهَانِ ﴾
[الرَّحمٰن: 37]

Then when the heaven is rent asunder, and it becomes rosy or red like red-oil, or red hide

﴿فإذا انشقت السماء فكانت وردة كالدهان﴾ [الرَّحمٰن: 37]

Al Bilal Muhammad Et Al
When the sky is rent asunder, and it becomes red like ointment

Ali Bakhtiari Nejad
And when the sky splits and it becomes red like the red rawhide (or red hot oil)

Ali Quli Qarai
When the sky is split open, and turns crimson like tanned leather

Ali Unal
And finally when the heaven is rent asunder, and it becomes rosy like red hide –

Hamid S Aziz
And when the heaven is rent asunder and then becomes red like red hide

John Medows Rodwell
When the Heaven shall be cleft asunder, and become rose red, like stained leather

Literal
So if the sky/space split/cut open , so it was a red/a rose as/like the paint/painted with oil

Mir Anees Original
So when the sky splits and becomes red like red hide

Mir Aneesuddin
So when the sky splits and becomes red like red hide