I don't think you should care about how the bag will look on you when you're older. Life is about now. Also, I think age stereotypes need to go. If you're confident in yourself and your aesthetic, tattoos, bright bag, there is nothing a number should stop you from doing.
The most important thing is how a bag in the colour itself ages. All bags look beautiful mint straight out the box, but there are colours that look great vintage and others that do not age so well. All the colours you are considering look great vintage - particularly the reds. Rouge casaque is a beautiful classic red. The only issue I have is that this colour is very common in epsom leather, which I think doesn't age so well. Of course that's just my personal opinion. Rouge Garance is a beautiful red as well, very classic; geranium is like RC with a little cream, here's a picture (togo)
Bleu Saphir will look darker and deeper in grained leathers and lighter in pressed & smooth leathers (epsom, swift, box), but I think the most important is the lighting. In the dark it will look very dark. Bleu Saphir could be a pop, but it isn't a very loud one.
My favourite ever colour in the blue/green family combined is certainly malachite. Its definitely a pop, but so versatile and changeable in the light.
GHW/PHW: If you want a pop, I would go with GHW. GHW brings out warmer, deeper tones in any colour and makes it look more classic and luxurious. A little more 'old world'. PHW can make some colours look flat and less bright in my experience, so its great for all-round, very understated neutrals. If you do love Bleu Saphir, one with GHW could totally count as an understated pop!
Malachite is also gorgeous with GHW, but louder than Bleu Saphir.
So...
red is certainly the loudest, but its a classic enough to not be OTT in any context, I believe. I think GHW enhances any red. Just my view, but Im not a fan of red + palladium. Too austere & cold.
Bleu saphir is understated, but can make a colour statement, especially with GHW.
Malachite is a gorgeous, multifaceted pop & you get the best of the worlds of blue and green. Most vibrant with GHW IMHO.
Good luck!