White and yellow is dated to me. Just my own personal hang up about yellow gold rings--very '80s to me (though I love yellow gold for earrings and necklaces, go figure). Now rose and white metal rings I love together.
Interesting how differently people feel about jewelry looking dated. I've had a couple of wedding set upgrades but keep them looking dated deliberately. I'm proud of how long we've been together and want my wedding sets to show it, dernit! Just realized I've never heard anyone else say that.
The most common thing I see where I am is a halo or solitaire, paired with a pave band, all in white metal. It's a pretty look but I love when I see something out of the ordinary. To my mind no color of gold really goes out of style, it's all in how you wear it or pair it.
For myself I cannot mix metals at all. All my jewelry matches a 14k YG bangle I was given as a baby. Which makes me sad because of I love the look of platinum and love mixed metals on others. But I tried it and seeing two different color metals together on myself is a no go for me.
I'm a mixer of only yellow gold and white gold or platinum, since I can remember probably when I was 16 and allowed to work (help in a department store in the jewelry section) guess that was where I started to love jewelry. I don't love all white heavy metal on my ears, I prefer yellow gold or more diamonds on the ears showing than white metal. As for rings, I love both, and have both, I did wear all yellow gold for the first 5 years of my marriage 24/7 and yes, it was the chunky type gold.
I really like the versatility of mixing metals. A lot of my "nice" jewelry is in yellow gold, but I have some cute pieces tiffany pieces that are silver that I never take off. So for me, mixing metals (especially stacking rings) is a nice way of making sure that I can wear whatever jewelry at any time.
I was reading a different thread about pave erings and whether they will soon be "outdated"- someone commented that all fads/trends come back around. So something to keep in mind.