Tandy announced the TRS-80 Color Computer on July 31, 1980. The initial model (catalog number 26-3001) shipped with 4K of Dynamic Random Access Memory (DRAM) and an 8k Microsoft BASIC interpreter in ROM. Its price was $399. Within a few months, Radio Shack stores across the US and Canada began receiving and selling the new computer.
Despite bearing the TRS-80 name, the "Color Computer" was a radical departure from earlier TRS-80 Models - in particular it had a Motorola 6809E processor, rather than the TRS-80's Zilog Z80.
The Motorola 6809E was a very advanced processor, but was correspondingly more expensive than other more popular microprocessors. Competing machines such as the Apple II, Commodore VIC-20, the Commodore 64, the Atari 400, and the Atari 800 were designed around a combination of the much cheaper MOS 6502, itself essentially an enhanced clone of the Motorola 6800.
The CoCo lacked some of the graphics and sound capabilities of other home computers, but made up for it in computing power and ease of programming in BASIC. Combined with the versatile BASIC, the robust, easy-to-interface-to design has long made it an experimenter's favorite. Enthusiasts have continued to affectionately tinker with the "CoCo" to the present day.
Source: Wikipedia, "TRS-80 Color Computer", available under the CC-BY-SA License.