The Grid

The Set

The set of triangles with zero to three hexagons, combined with the set of hexagons with zero to six triangles.
One element features in both sets - leaving one of this pair out renders the "single set". If instead all single pieces are doubled, we get the "double set", with triangles in two colors.
The Idea

A single set in a solution featuring triangles in two colors.

Two double set a solutions.

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