The facets declared through Algolia Shopify plugin can be configured to be "searchable", "conjunctive" or "disjunctive".
You can head to Algolia Shopify Configuration > Search Options tab >
InstantSearch - Results page powered by Algolia > scroll down to "Facets" section and edit the relevant facets by hovering over them and clicking "Edit".
In the dialog box which opens, please check "Searchable facets" / mark it as conjunctive / mark it as disjunctive