The Otsutsuki don't have the Sharingan, so that means that the Sharingan is an alien mutation, a unique genetic hybrid dojutsu unique to humans that originated from a combination of human and Otsutsuki DNA.
It's interesting that the Byakugan genetically transferred to Kaguya's descendants unaltered with its usual properties, yet aside from Hagoromo, Kaguya's descendants didn't directly inherit the Rinnegan, but rather an entirely different hybrid dojutsu. While the Sharingan can eventually upgrade into the Rinnegan under extremely unique and rare circumstances, and only for Indra's reincarnations, for most Uchiiha, the Eternal Mangekyou Sharingan was as far as they could go in leveling up their Sharingan.
Hagoromo was the first human to possess the Sharingan (naturally, being the son of Kaguya as well as the father of Indra Otsutsuki, the ancestor of all Uchiha) as well as the Rinnegan. Since Hagoromo's Otsutsuki blood was far less diluted than that of his descendants several millennia later, the descendants we see in the era when the Naruto series takes place, it should be noted that the rules and conditions for Hagoromo's dojutsu vary and differ a bit due to having a higher concentration of Otsutsuki blood.
The Sharingan is not a given ability, since merely being born of the Uchiha bloodline isn't enough to possess a Sharingan. They have to be awakened by a specific emotional response (with the Mangekyou Sharingan demanding the most specific set of circumstances of all).
The Sharingan grants its user many different abilities, with some of its basic functions including the ability to watch and then instantly copy others' movements and jutsu, to detect and predict the flow of an opponent's movements so they can easily dodge attacks, and the ability to cast genjutsu. It grants them the ability to see far, to see through walls, to see chakra (and the different colors of chakra), and even to use the Sharingan as a microscope and view things on a cellular level. It can read minds, search memories, and even erase memories, among other things.
The Itachi novels once mentioned that the Sharingan tints one's vision with a reddish hue, though how accurate or consistent this is is unclear, since it seems that there are different vision "modes" to the Sharingan, so it seems like it might be possible for a user to switch between modes, so they can either focus on predicting their enemy's movements or on looking at other people's chakra, or reading someone's mind, like Sasuke does when he invades Naruto's mind when he first meets Kurama.
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So if the Sharingan actually tints a user's vision red, I don't think that the Sharingan's vision is always tainted a reddish hue (though it certainly could be and we just aren't ever shown the Uchiha's visual POV in the anime). Plus that's a novel and certain details from the novel are not necessarily always the most credible, even if I'd consider the Itachi novels mostly canon overall.
Although I think that when an Uchiha activates the Sharingan, they intentionally have to look for chakra flows to see them. Otherwise, it would be weird for characters like Sasuke, Sarada, and Madara to not register the change in their eyes right away when they awakened their Sharingan if their vision was so different; they should have noticed their newfound ability to suddenly see chakra or the red tint to their vision. So that tells me that these abilities require a bit of effort, and the way the Sharingan's activation changes vision isn't necessarily noticeable to its user.
