Complex sentence: The undersides of the wings of both sexes are highly variable and no two specimens are exactly alike, though the colors are always those of dead leaves like gray, brown, red, olive green, or pale yellow.
Split into simpler sentences: The undersides of the wings of both sexes are highly variable and no two specimens are exactly alike. However, the colors are always those of dead leaves like gray, brown, red, olive green, or pale yellow.