Changing color inside a non-solid 3d floor

Title explains it pretty well, I want to make a pool of liquid using a non-solid 3D floor (I don't want it swimmable) and have a slight color offset when inside the pool. How do I go about this?

Change the color and / or fade in the control sector for the 3D floor.

Just as Emprye said, you have to either use ACS to change the color of the dummy sector or if you're using UDMF you can change the custom sector properties to set the color you want.

In Legacy, you could also do this by setting a hexadecimal RGB value in the control sector's sidedef, IIRC - something like #208020 for a dark-green auto-generated colormap.

This could also be achieved with Boom's type 242 transfer properties 

No. Those set an entirely different property. Do not be fooled by Eternity inheriting SMMU's 'rework' of the feature, that's not how it was supposed to work.

2 hours ago, Graf Zahl said:

No. Those set an entirely different property. Do not be fooled by Eternity inheriting SMMU's 'rework' of the feature, that's not how it was supposed to work.

 

@Graf Zahl: Are you referring to how type 242 works in Eternity? In other words, did Eternity inherit a reworked SMMU linedef 242, or were you describing some other feature that was reworked in SMMU, then inherited in Eternity? (I am, of course, interested in seemingly identical effects that actually work differently in different ports). Can you be a little more specific?

3 hours ago, Graf Zahl said:

No. Those set an entirely different property. Do not be fooled by Eternity inheriting SMMU's 'rework' of the feature, that's not how it was supposed to work.

 

I interpreted OP's "inside the sector" as meaning when the player was inside the sector i.e. Underwater. That's exactly how Boom did it. I am aware that Eternity historically did it different/wrong (as did indeed zdoom).