Well, I have opinions on all sorts of stupid inconsequential things. Just like every blogger that ever did blog (god we're annoying). So here is my totally unsolicited advice about your underwear: Stick to a color scheme. If you're going monochromatic, make that color "nude/flesh tone". You don't have to worry about it showing underneath light colored clothes that way, ever. Your bra(s) will match ALL of your underwear, no need to worry about finding matching pairs. It's kind of like how all your shirts should be able to be worn with all of your pants in a travel capsule. Well, your bra(s) and panties should all be able to be paired with each other and match. (Unless you don't care about clashing undergarments, like some sort of neanderthal. I don't think we can be friends.)
I chose black and nude, mostly because I don't own enough nude undergarments to last for an extended holiday like my 5-week European foray. But you'll notice that a lot of my black undergarments are a combination of black-and-nude, which meant they can easily be paired with my nude underwear. So it still worked, when it came to coordinating all of my bras to match all of my underwear/panties (I hate the word "panty". Sorry. I prefer to just call them underwear, as inelegant as that sounds).
This may seem like a really minor thing, but when you're living out of a suitcase, it becomes surprisingly pleasant to not have to think about clashing underwear, or realizing that the turquoise bra you are wearing only has one matching underwear and it's dirty so now you need to either change bras or have mismatched underwear. Or maybe normal people are not bothered by that, but I am. And if you are too, now you know how to avoid it when on holiday. And real life. My underwear drawer has this exact same color scheme by the way. I dislike clashing THAT much. (I can't believe I actually argued with my doctor over his diagnosis of my mild OCD. But I WOULD argue with a doctor, wouldn't I?)
Another tip: if you're on an extended holiday, bring a small bottle of Woolite (or some other detergent that works well in cold water). Undergarments are small and dry quickly, so you can easily handwash these items in a sink and hang to dry on the shower bar or towel rack. There is absolutely no reason to bring more than a week's worth of underwear, or more than 2 bras no matter how long the trip. I brought one nude bra, and one black-and-nude bra, and all 7 pairs of underwear were nude, black, or nude-and-black, and was completely fine for over a month. I could even have left one of the bras at home, in all honesty.
The moral of the blog post is: Stop overpacking underwear. Stick to one (or two at most) colors and make sure it all mixes and matches together. Done.