The colonization of Mars and the relocation of a significant portion of the human population would not have a noticeable effect on Earth's orbit. The mass of Mars, even with the addition of human colonies and infrastructure, is minuscule compared to the mass of Earth.
Earth's orbit is primarily determined by the gravitational force between the Sun and Earth. The gravitational pull of other planets, including Mars, contributes to the complex dynamics of the solar system but does not significantly affect Earth's orbit. The mass of the entire human population is also negligible compared to the mass of Earth. Therefore, any changes in the distribution of human population or infrastructure on Mars would have an insignificant impact on Earth's orbit.
It's important to note that Earth's orbit is governed by numerous factors, including the gravitational interactions between all the celestial bodies in the solar system. However, the distribution of humans on Mars would not be a significant factor in altering Earth's orbit.