...
HY_Domain > Node Params > Display > Property > Splash/Foam preview
Once you have enabled the preview function, it is possible that the fluid particles will show a uniform colour. In this case please go the next or previous frame. After a few seconds (this depends on the number of particles), the fluid's viewport representation should change. Here, the splash- and foam-emitting particles are displayed as white dots:
Now you can start adjusting the associated threshold parameters to see and evaluate the splash or foam emitting areas:
...