my color is rainbow

Artists would use creative lighting and shots to mask the lack of a budget. The general visual aesthetic was gritty and less clean. Sometimes downright grimey. You'll notice that they kept action scenes minimal and instead used grand panning shots focussing instead on the scale of things and intricate lighting and detail in hand painted scenes for 03. This worked even better with the more philosophical edge of 03 compared to bh. 03 has a lot of stand around and talk scenes in it that give you important points in the characterization, the fights are usually short and extremely impactful, think the final fights between Ed and Envy and Ed and Greed. Even towards the end when 03 got a massive budget from how well it was doing the art direction pretty much stayed the same just with better and more fluid action sequences and a nicer op animation. This is true for pretty much all the anime of the time.

The art and character designs were also a lot more busy at the time so you'd see a lot more fabric animation.

Bh came at a time when art was a lot more simplified and colours became a lot less saturated. That combined with Arakawa's...very specific art style meant that the colours were a lot more vibrant and the character design was rounded and flattened. Her art style doesn't translate the same way to anime as the old school rough art used to. And with so much budget, so many advancements in animation techniques the animators basically just started flexing how much they could animate. Suddenly you could see everything and that was a flex because every single thing could be right in front of you without needing dramatic lighting to hide the flaws or drawbacks behind. They also seemed to animate the scenes 1:1 to the manga panels which works great for a manga, not so much for an anime because the mediums require different approaches to how shots are laid out. Angles and lighting matter a lot in anime. Or really anything on the screen. Bh suffers from trying too hard to be true to the manga which means much of it falls flat in execution but also from too much budget which means the animators were acting more like kids showing off everything they could do now which meant that there was no need for dramatic lighting or anything of the sort. Meanwhile 03 was being endlessly creative on a shoestring budget so we got iconic shots because they had no choice.

That's not to say that bh was completely faithful to the manga either because there are a lot of action shots in 03 that just shift the angle slightly and add a lot more to the scene.

(Volume 10 chapter 7)