Need a rough UI design for 3 grids with many to many relation

Need some help here to design a container having 3 lists(grids) communicating with each other as below:

3 Lists communicating with each other

The requirements are:

  1. There are multi select allowed on each list.
  2. On selecting customers, associated product and services wll be filtered.
  3. After refresh all and selecting products will refresh(filter) associated customers and services.
  4. On multiple selection on any entity, associated entities should be distinguished(top-bottom or bottom-top hierarchy)( I did it by color here).

In my way, my problem is a particular scenario: When selecting 2 or more products, if they are associated with same customer, I will not identify which color I should give that customer entity.

Is there any other UI design which can accomplish the need? Just an sketch will help.

Thanks.

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