I find the gold jewellery to not look that great on Aura, since it blends too much with her skin colour (could say the same about her hair and dress). It might be different "in real life" since it'd have a metallic shine, which isn't visible in a manga. For Freya I think it'd work if it was a darker gold, rather than a brassier yellow, but it also depends on whether you want to accentuate her paleness or make her look warmer.
Going by the setting and location of Capua, in real life she would most likely have an olive complexion. This usually mean that rose is a good colour (rose fits with almost anything) or a lighter shade of gold. Although to be sure you'd also have to look at the skin undertone, not just the complexion itself.
For Freya gold is really not the best choice, no matter the shade, gold is too similar to yellow (in vexillology they are even considered the same). Silver, with colourful gems is better.
You don't even have to go outside Western clothing. European Medieval clothing was quite colourful, despite what a lot of media portrays it as.
Citizen clothing, with emphasis on the citizen, i.e. the modern suit that came after the
Great Male Renunciation, which, apart from the neck-tie is usually quite dull. According to Anglo-German psychologist John Flügel, men "abandoned their claim to be considered beautiful" and "henceforth aimed at being only useful". This phenomenon lasted roughly until the late 1960s (Protests of 1968, counterculture, that sort of thing)
The red isn't consistent, looking at the covers, though on my screen it doesn't look that deep or dark.
Don't look at the highlights and instead look at the more shaded areas. Take the cover for Volume 8; the best place to get the "actual" colour for her dress would be the centre of here breasts, directly below the border between light and dark. Don't take the opera gloves and or the cloth belt, those are darker shades of red (could be burgundy or maroon). Naturally you can't get the exact colour, since any 2D image is missing (or only approximating) reflections for the weave and highlights or subsurface scattering.
The difference in skin tone between northern and southern Europe is less than the individual difference.
I wouldn't consider an Olive complexion (e.g. Greeks) the same as a fair complexion (e.g. Swedes), but the point wasn't about complexion, it was about clothing and yes the difference is there, although it's not as massive as say for example, Germany and the Kongo.
The thing about that, taste is far from universal.
Although people think they are individualists, most human behaviour can be described by probability distributions, and quite narrow distributions at that. This is how societies form, liking and disliking the same things. That's the reason why we know which colours go together and which do not; despite cultural differences (e.g. which colour to wear at a wedding), there's a background noise that is present across humanity. The aforementioned rule of thumb is such a background noise.
The main problem with that is that limits you far too much in what you can wear.
Apart from massive occasions like a coronation, its far less limiting than one might think. Take Aura for example: She's not going to strode around with all the crown jewels, in fact it would be very weird if she wore them at all. That's why there's two crowns for the British monarch, bot to be used at different occasions. You can really see how much you can do with clothing in an restrictive environment if you look at the late Elizabeth II. Highly varied clothing with specs of state regalia mixed in. Even at highly formal events like Opening of Parliament she wasn't restricted at all.
The men in the royal family had it far less good, usually uniform or bust. But that's a general theme, (modern) men's formal wear is quite boring.
The cover for the next volume (which is already up on the manga page) shows Freya in said red dress. It's the same colour as Aura's, complemented with silver jewellery.
