#775F55

hexadecimal - base 16

binary base system
octal base system

0123456789ABCDEF

two decimal digits -- 100 diff values

two binary digits - 4 different value
00
01
10
11

two hexadecimal digits - 256 different values
16 x 16 = 256
2 ^ 8 = 256

colors often stored as RGB
255
0
0
pure red

0
255
0
pure green

0
0
255
pure blue

0 - 00
0
0
black

255 - FF
255
255
pure white