Woah! Wow! Oh my! Subtractive Lighting (maybe), IN ROBLOX?
Hard? No, it’s surprisingly easy, unless you forgot how to use a keyboard. Just put a negative number in the Color property of any light et voilà!
Functionality
You can also recreate the “normal” colors by mixing negative values (SUBTRACTIVE COLOR MIXING REFERENCE?) (I think I made a mistake on the red light in the image, should be 0, -255, -255 lol)
Also, look at how sharp the lighting is!
Imagine using regular light colors in 2028. This is the future, ladies and gentlemen! (not really)
You can even “block” normal lights with this brand new™ lighting™ technology or, if you are feeling generous, you can let only some lights inside the negative light
So this is what they meant by black LEDs? It honestly could work for some kind of black hole effect, since it eats all the light away (including the sun light)
The Shadows property also works, allowing you to create an “inverted shadow” effect! Very epic™!
Also looks like some kind of flashlight?
You can also mix positive and negative Color values which also kinda looks cool
Removes green light while emitting red and blue light (I know this is kinda complex, especially for a low brain cell individual like me)
Use cases
Here’s a fun scene I made with these lights, very fun:trade_mark:! 
Did someone just awaken ME? The ancient moai of wisdom?
(NO SPECIAL EFFECTS BY THE WAY! Just some new™ lighting™ technology, made using a -255,-255,-255 colored Pointlight, and a red Pointlight)
How it probably works?
Now, I’m no technical expert. I don’t have the code to Roblox’s lighting engine and even if I did, I probably wouldn’t have the brain capacity to understand it. But my (un)educated guess on how this works is:
Lights mix in Roblox, similar to how real world lights work, but because Roblox didn’t add any limits to the Color property, we are able to set one or more of the RGB Color values to be negative and have the light delete those specific Color values within its range.
The reason they most likely don’t have a fade effect near the edges of the light is because Roblox probably didn’t account for negative colors. They are probably using a mathematical function that doesn’t take negative numbers (e.g. square root)
How to (just in-case you have a short attention span)
STEP 0.5: Set Lighting.Technology to FUTURE
STEP 0.99: Make sure your graphics settings are set to high
STEP 1: Insert a light (e.g. PointLight) into a Part, Attachment, or where a light can render
STEP 2: Set one or more of the Color values to a negative value (e.g. -255,0,0)
STEP 3: Configure any property as you like
Setting Brightness to 0 disables the light effect
Fin
Honestly, I think Roblox should keep this, because this is actually a very, very cool (though most likely unintended) feature. Getting rid of this would just mean more limitations and less creativity on this platform. I can see a lot of Roblox games taking advantage of this for many use cases, such as horror games, or just creating interesting visuals and artwork in general. Unless a Roblox employee states that they won’t be patching this…
USE IT WHILE YOU STILL CAN AHHHHHHHH
By the way, these types of lights only work on the “Future” lighting technology. Any other technology as of now does not achieve this effect.
