Monochromatic parallelograms of prescribed area
Determine whether every finite coloring of the plane contains a monochromatic parallelogram of any prescribed positive area.
References
The analogous question for parallelograms of prescribed area is more tricky and remains open .
— A 21-Coloring of the Plane Without Monochromatic Unit-Area Rectangles
(2609.00583 - Hu et al., 1 Sep 2026) in Introduction, immediately following Theorem 1