We have *~several~* redheaded characters to choose from, anon! Age is relative tho, there’s youngest in actual years, then there’s youngest in appearance.
****Opening my overcoat to reveal the gingers****
The Vampire Armand
He’s probs your best bet, being the youngest in appearance, he was turned into a vampire when he was 17. He’s one of the main characters and pretty easily recognizable even to ppl outside VC fandom. He’s over 400 yrs old now. Other characters often compare him to the youths in Botticelli’s paintings; so pretty, he mentions that he’s mistaken for being a girl at least once in his mortal life.

[^Portrait of a Young Man 3., Botticelli, and I think the expression is very Armand, he’s pretty much the sassy teen of the series but as grumpy as an old man]
I would never be anything but the seventeen-year-old boy you see now… [but] I am not a waif and never have been. I am a strong child. – Armand, The Vampire Armand

^X @amadeo-child-of-the-renaissance found this, another Botticelli angel Armand, with a face that’s more canon-compliant IMO 😉 AR bases Armand off these Botticelli angels and they have varying straight and curly hair, usually wavy at least.
Armand’s hair is described as curly when he was mortal and when he was a fledgling, so I think that’s the natural state of it.
Armand can be dapper or grungey depending on his mood, so the crucial aspect is really his hair, and if you want extra credit, you may want to carry a blender around, that’s sort of the fandom joke about him and Daniel going nuts over blending stuff in QOTD.
Here’s some Armand cosplayers (they’re mixed into that link) you might wanna check out 😉
Other redheads in the series… bc I don’t wanna hide the rare VC ladies under a cut! NO CUTS WE LONG POST LIKE MEN

^I’m not wild about her portrayal in the QOTD movie but anyways… she’s a little over 30 when she’s turned, and it was 1985, so she is technically younger in age than Armand. He will always look younger than her, tho.
Cosplaying Jesse Reeve would involve smtg about her being a Talamascan, maybe, or carrying Claudia’s diary? She finds it in QOTD.
^The redhaired twins. You might go to @redhairedtwin, a Maharet RPer, for descriptions of the twins.

^X Maharet (left) and kid!Jesse (right) in the QOTD movie. I headcanon Maharet and Mekare as being younger in appearance than we see Maharet in the movie, but idk right now how old they were when they were turned (I don’t have my books to check either). Early 20′s, early adulthood, I think. Maharet and Mekare are technically the oldest on this list but they might look the same age or younger than Jesse.
Cosplaying one of the twins means a bloody mouth or bloody eyes.

^poor Madeleine in the the IWTV movie barely had any screentime, she got a little more in the book, but she’s rarely mentioned in later canon. Louis’ first fledgling, made to take care of Claudia so he can go bang Armand move on with his afterlife. She’s a more obscure character, but she’s A REDHEAD SO SHE COUNTS!
If you want to cosplay her, carrying a doll that looks like Claudia, or wearing a locket with a portrait of a Claudia look-alike, that’d be a good accessory 😉
I think that’s all the relevant redheads in VC, but if anyone can think of more, feel free to reblog and add!