No, it is not currently believed that gravity is a long-distance effect of the strong force. The strong force and gravity are two distinct fundamental forces in physics, with different properties and behaviors.
The strong force, also known as the strong nuclear force, is responsible for holding atomic nuclei together. It is a fundamental force that acts between particles called quarks, which are the building blocks of protons and neutrons. The strong force is much stronger than gravity but has a very short-range, meaning it operates only at extremely small distances within the atomic nucleus.
Gravity, on the other hand, is a fundamental force that acts between all objects with mass or energy. It is responsible for the attraction between massive objects like planets, stars, and galaxies. Unlike the strong force, gravity has an infinite range, meaning it acts over vast distances.
While it is true that the Higgs mechanism, associated with the Higgs field, is responsible for giving particles mass, including quarks, it does not directly relate to the gravitational force. The Higgs mechanism explains the origin of mass in the context of the electroweak interaction, which unifies the electromagnetic and weak nuclear forces, not the strong force.
Theories attempting to unify gravity with the other fundamental forces, such as grand unified theories (GUTs) or theories of quantum gravity, are actively pursued in modern physics. However, currently, there is no widely accepted theory that successfully combines gravity with the strong force in the manner you described.