This addon provides a blend mode that mixes colours the same as the built-in "multiply" blend mode, however, it is only applied when the underlying colour is pure white (#ffffff).
This can be used along with the "ZX Spectrum Paper" addon to recreate the ZX Spectrum aesthetic in Construct 3.
Since the foreground colour is only applied when the underlying colour is white, you can safely stack objects and layers with this effect.
See the devlog for more information about how it works (https://little-martian.dev/21-07-05-construct-3-zx-spectrum/) and I recommend you try out the example project to see it in action.