Some translations set quotations from the Old Testament farther to the right on the page to make them easier to read. The ULB does this with the quoted words in verse 7.
The Bible often speaks of something that belongs to a person as being "white." This is metaphor and metonym for that person living rightly and pleasing God. (See: [[rc://en/ta/man/jit/figs-metaphor]] and [[rc://en/ta/man/jit/figs-metonymy]] and [[rc://en/tw/dict/bible/kt/righteous]])
Blood is a metonym for death. Jesus "has released us from our sins by his blood." John means that Jesus saved us from our sins by dying for us. (See: [[rc://en/ta/man/jit/figs-metonymy]])
Jesus went into the clouds when he went up to heaven after God raised him from the dead. When Jesus returns, he will also be "with the clouds." It is not clear whether he will be sitting or riding on clouds or coming in the clouds or "with the clouds" in some other way. Your translation should express this in a way that is natural in your language.
This refers to Jesus. You should translate the words "son of man" using the same words as you did in the Gospels for when Jesus called himself the "Son of Man."
The word "angels" here can also mean "messengers." This might refer to heavenly beings, or to the messengers or leaders of these seven churches. John uses the same word "angel" (singular) in verse 1 and in many other places throughout the book. Your translation should also use the same word.