ANSIエスケープシーケンス 仕組み
0x1B Starts all the escape sequences
ESC[<color>m<text>という形式になっている
colorはnumber
たしかに、通常の文字列では表せない感
CSI: ESC[
For Control Sequence Introducer, or CSI, commands, the ESC [ is followed by any number (including none) of "parameter bytes" in the range 0x30–0x3F (ASCII 0–9:;<=>?)
SGR: CSI<num>m
num=0はreset
30–37 Set foreground color
40–47 Set background color