Tachikoma are based off the Fuchikoma that appeared in the original Ghost in the Shell manga by Shirow Masamune. However, they are not the same type of mobile combat support units. Rather, the Tachikoma are a bit taller, and have multiple lenses, while the Fuchikoma from the manga only had one lens.
As far as the Artificial Intelligence goes, some fans have observed that the Tachikoma seem more human-like, and thus more willing to defend their human counterparts in Section 9, while the Fuchikoma were more serious.
Most of the Tachikoma that appeared in Ghost in the Shell: Stand Alone Complex and 2nd Gig are painted blue, but a few get repainted silver and yellow. They are sometimes equipped with different weapons to suit their purpose, such as a Gatling gun.
The subsequent series of AI-equipped combat support vehicles are the Uchikoma. They appear to be a hybrid between the manga’s Fuchikoma and the anime’s Tachikoma, utilizing a horizontal “body” and a single lens (from the Fuchikoma) and the four legs (from the Tachikoma). The Uchikoma is painted a standard military green.