Let's recreate the look of classic 3D movies from the 1950s with this quick and easy Photoshop effect! The following step-by-step instructions are for Photoshop 2023 or earlier.
Of course, because Photoshop works with flat 2D images, we're limited in what we can do. But at least it's possible to create something that looks like it's from an old 3D movie. And as we'll see, this effect is so easy to create that you can do it from start to finish in just 60 seconds or less.
Step 1: Create a copy of the Background layer
In the Layers panel, the image will appear on the Background layer:

Make a copy of the Background layer by dragging it down to the icon New Layer.

Photoshop adds the copy on top of the original.

Double-click the copy's name to highlight it.

Then rename it to “3D”. Press Enter on a Windows PC or Return on your Mac to accept.

Step 2: Open Photoshop's Blending Options
Still in the Layers panel, open Photoshop's Blending Options, by double-clicking the empty gray area of the “3D” layer or clicking the fx icon at the bottom of the panel Layers:

And select Blending Options from the top of the list.

The Layer Style dialog box opens with Blending Options in the middle column.

Step 3: Turn off the Green and Blue color channels
In section Advanced Blendinglook for the R, G, and B checkboxes next to the word Channels.

R, G, and B represent the Red, Green, and Blue color channels that Photoshop mixes together to create all the colors in the image.
Turn off the Green and Blue channels by unchecking the G and B boxes, leaving only the Red channel (R checkbox) enabled.

Then click OK to close the Layer Style dialog box.

Nothing will happen to the image. But if you turn off the Background layer by clicking on that layer's visibility icon:

You'll see that the image on the “3D” layer is now only showing in red.

Turn the Background layer back on to return to the full color image.

Step 4: Select Move Tool
To create the red and cyan 3D effect, all we need to do now is offset the two versions of the image.
In the Layers panel, make sure layer “3D” is active.

Then in the toolbar, select Move Tool. We won't be using the Move Tool, we just need it to work.

Step 5: Gently push the image to the left
Use the left arrow key on your keyboard to gently push the image on the “3D” layer to the left. Hold Shift while pressing the arrow keys to move the image in 10 pixel increments.
As the image moves, a red border appears along one side of each object. And since red's opposite color is cyan, a cyan border will appear along the opposite side.
The more the two images are offset, the thicker and clearer the red and cyan outlines will be. So keep pushing the image gently until you're satisfied with the result.

Try other color combinations
Along with the classic red and cyan 3D colors, you can also choose other color combinations to create different effects.
In the Layers panel, open Blending Options again by double-clicking on the empty gray area of the “3D” layer.

Green and magenta
Then, in the Layer Style dialog box, uncheck the box R to turn off the Red channel and check the box G to enable only the Green channel.

This gives you a green and magenta effect (because magenta is the opposite color of green).

Blue and Yellow
Or turn off the Green channel and turn on only the Blue channel:

For the blue and yellow effect (yellow is the opposite color of blue). To go back to classic red and cyan, simply uncheck both the Green and Blue channels, then turn the Red channel back on. Then click OK to close the Layer Style dialog box.

And that's it! It's easy to recreate the look of classic 3D movies in Photoshop.