This coloring titlebars, introduced in 5.24 and toolbar/window/icons in 5.25...myeah..it's still a mess. I'm not sure what code exactly is being used but I read a lot of issues on several forums of colors not correctly applied. Wrong border colors, faded colors etc...
Anywho, I don't use the stuff, I don't like it. It messes up quite a bit a custom user gui stuff. Now, to begin with, I don't use default Breeze. Not the application theme, the window decoration nore the icon theme. Personally I use Lightly and Klassy window decorations. Now, if you start putting together some custom color schemes, you'll notice that the border and icon colors are off if you should use the breeze color scheme and icons. I discovered that, in order to have their coloring thingie to work, they "ommited"/"added" some lines within the color schemes. Simply put, you cannot have a active header section in the color scheme. If you don't want a descripancy in the theming, only the inactive header section can be in your color scheme. Something like this ( preferably in ~/.local/share/color-schemes)

[Colors:Header][Inactive]
BackgroundAlternate=227,229,231
BackgroundNormal=239,240,241
DecorationFocus=171,188,200
DecorationHover=171,188,200
ForegroundActive=171,188,200
ForegroundInactive=112,125,138
ForegroundLink=41,128,185
ForegroundNegative=218,68,83
ForegroundNeutral=246,116,0
ForegroundNormal=35,38,41
ForegroundPositive=39,174,96
ForegroundVisited=155,89,182

That's one. Secondly, the icon coloring is not correct. It's not such a big deal but, clearly, something is wrong. It will happen in default breeze and breeze RC. This is what I mean:https://imgur.com/a/UkCaUkN Personally, I use both Chameleon Breeze and Chameleon Breeze RC. Those two DO apply the correct coloring based on the scheme's highlight. This:https://imgur.com/a/v8D3Yuf. As does a custom icon color script ( although that depends more on the color setting in the script, I'm just saying): https://imgur.com/a/mmPeSUh

So yeah. I noticed that in a pure default setup, breeze light coloring was kinda ...off. Adjusting the color scheme did the trick. But overall, if you use other than default breeze application, window decoration and breeze based, those are some options.

PS: As far as gtk goes...that's another story. If you want consistancy in gtk apps, you'd probably have to make your own gtk theme ( I suggest oomox). Because the Breeze window decoration ( border color) will be different than the theme itself https://imgur.com/a/R10xIpn. Myself, I like my browsers dark. In the screenshot it's a homemade gtk which uses the same homemade colorscheme. So, in this case, the browser is launched with the gtk exec like: Exec=env GTK_THEME=oomox-CakeDark /usr/bin/brave-browser-stable %U and the window rule is set to use the same color scheme border.https://imgur.com/a/qYc5Ehj
The entire point of this post is to have an overall consistancy, wether you use Breeze, Klassy, Lightly, gtk override or qt override which, imo, doesn't work well in the latest default breeze. https://imgur.com/a/4bf4d80

Myeah. I hope KDE devs will incorporate a on/off switch for this..um..highlight coloring..um..let's call it "novelty" in the near future. First of all, I don't like the 90's style breeze application style and I don't use it. Neither do I use breeze window decoration and default breeze icons. Personally I use Lightly application style, Klassy window decorations and Chameleon ( both regular and rounded) icons. See, with the intro of this highlight/coloring..whatever, the Lightly application style partially breaks. Sure, you could say that it's up to the designer of Lightly to adapt his code to this new...half baked gnomish ui customization OR, just maybe, KDE devs could incorporate it altogether alongside the Oxygen, Windows (?!?!), Breeze or Fusion options. It shouldn't be too hard. A, formerly third party tiler like Bismuth can be found in the repos nowadays for example. Just sayin', I like to set up my stuff the way I like. That "omg soooo awesome highlight/coloring" increasingly disables that possibility. Yeah, a turn-off switch or an application style option would be nice.
https://imgur.com/a/bxhiPuD