I think that you need to re-read "escape sequences" and "American National Standards Institute" a few more times until it clicks that these are two entirely different noun phrases.
Then you need to learn a lot more about control sequences.
You can start with CSI, value 0x009B, not being an ASCII character. Then proceed to ITU T.416 (ISO 8613-6) where the SGR control sequences for indexed and direct RGB colours are standardized. Then you can learn that the "E" in ECMA-48 does not stand for "ANSI", but for "European". And finally you can discover that ECMA-48 standardizes exactly 8 colours. 16 colour SGR sequences beloved of CGA-like and VGA-like art are not in the standards and are in fact the product of IBM's AIXterm.
Then you need to learn a lot more about control sequences.
You can start with CSI, value 0x009B, not being an ASCII character. Then proceed to ITU T.416 (ISO 8613-6) where the SGR control sequences for indexed and direct RGB colours are standardized. Then you can learn that the "E" in ECMA-48 does not stand for "ANSI", but for "European". And finally you can discover that ECMA-48 standardizes exactly 8 colours. 16 colour SGR sequences beloved of CGA-like and VGA-like art are not in the standards and are in fact the product of IBM's AIXterm.