PC Engine (TG16) games are so colourful! I wish more modern games use bright colours like they used to do.

One of the things I really enjoyed about Marathon (versus Doom or Quake) is that Marathon had colours outside of brown, reddish brown and greenish brown.

It wasn't an engine limitation, it was a design choice. Heretic is a colorful game, and it was made using Doom engine.

It's especially bad in Quake, all monsters look like a moving piece of a wall, and the level design is walls on top of walls with some walls in-between. If not for the revolutionary game engine, it would seriously flop.
- Oh, I don't disagree that it's a design choice. 1990s id Software had, we'll, let's not call it a style...

Yeah lemme get a hit of what you're smoking... I would argue modern games have a heavy over saturation of ridiculously colorful games. Look at the popular titles of like every major genre within the last few years and tell me that's not the case.

Shooters- Fortnite, Valorant, Apex, The finals, Splatoon (cod being the only major shooter with a drab palette)

Car/Racing- Mario kart, Forza, rocket league, that one game everyone overlays on TikTok videos with the crazy winding tracks

Fighting- Street fighter, Tekken, MK, Smash, Guilty gear (all very colorful or at least significantly more colorful than the previous iterations)

Indies- Hades, hollow knight, cult of the lamb, pizza tower, stardew valley, undertale, subnautica, vampire survivors, ori

Pandemic hits everyone obsessed over, among us and fall guys.

Marvel snap is the biggest entry into the card game market, which has been dominated by none other than Hearthstone for a while now.

The only genre I can think of that doesn't have an excess of color is rpg's, with the new Zeldas, baldur's gate 3, starfield, elden ring, last of us, etc being a bit neutral, (still not dull by any means) but even with that being said things like spider man, palworld, and cyberpunk exist.

Anyway, yeah this list got a lot longer than I planned but I think it illustrates my point.

There was definitely a period in the Xbox 360/PS3 era where everything was a drab grey and brown with a godawful bloom effect on everything. We do seem to be past that now, thankfully.
Might also have to do with the display used - games are mastered for HDR and SDR, and I find that I have to be much more precise with color correction than I was with older games; Helldivers 2 needs more saturation in game for me
- Also, perceived contrast varies widely between the different types of LCD monitors

Question that might sound dumb.

Were they actually this vibrant back then or were they made more vibrant to make up for limitations of a CRT?

Little bit of A, little bit of B. The sprites were also designed with CRT limitations in mind so they generally look better than they do on non-crt screens
- Things like stippled dots or vertical lines especially would blur into each other making new colours or faking transparency.
  
  Random video to demonstrate it. https://www.youtube.com/watch?v=IthGu6Ysmpc
  
  But if your TV was too good, you wouldn't get the effect as much.
Nope, they weren't. But there were definitely differences whether you played on a Sony Trinitron or a cheap TV. Hell, I even played some games on black-white-TV when the color TV wasn't available.
The system could only display 400-something colors at a time. Once you reduce the number of colors that can be used, you lose gradients so one color doesn't ease into another color. Due to this, art styles were typically different and used contrast to "pop" the characters and items visuals in game since being more realistic wasn't an easy (or possible) option.

Now that we can have millions of colors, you can do whatever style you want.

A similar thing happened as polygon counts went up.

The answer is 256-color (8-bit) palette.

You guys should check out OpenBOR, it's an open source game engine for beat'em-ups. (It uses 256 colors at max per game so they're pretty colorful).
- Isn’t that the dragon from Demon’s Crest?

Now way! Give me Fallout 3's atomic drab brown all day. /s

I had to play Fallout NV with mods so I could neutralise the piss filter.
- Fallout 76 was a nice change of pace, graphically. It was crap gameplay at launch, but it sure was pretty. I wonder if it's worth another playthrough now that it has human NPCs and raiders and such.
  
  Hell, I don't even know what platform I bought it on and if my account it still active.
Fallout 3 at least has a context: nuclear apocalypse. And New Vegas is in a sparse desert.

Every other FPS going with shit brown as a theme, like an entire generation of Call of Duty games.
- Thing is, 200 years after a nuclear apocalypse the whole world would be green.

If you haven't played it yet, OP you may really like Ultros.

Classic feeling metroidvania, modern game engine, but it's visuals are fucking amazing and the colors, oh man.

They went for this incredible psychedelic art style and it's just gorgeous and vibrant.

https://youtu.be/AyGZAzHu1QQ?si=AdEjVo3pjHZ-MuFn

Here is an alternative Piped link(s):

https://piped.video/AyGZAzHu1QQ?si=AdEjVo3pjHZ-MuFn

Piped is a privacy-respecting open-source alternative frontend to YouTube.

I'm open-source; check me out at GitHub.

Not too similar to these titles, but this is why Robotron 2084 (arcade game) has a special place in my heart. Beautiful, smooth phases of vibrant colors with each level transition, and awesome sine/saw wave sound effects too. It’s addicting.