Hexadecimal ?

Question

Can any body tell me about Hexadecimal
How can i use them to define thousands of colour?

Answer 1

Check this out:
 "Colors HEX"
https://www.w3schools.com/Colors/colors_hexadecimal.asp
and this too...
"RGB Colours"
https://www.w3schools.com/colors/colors_rgb.asp

Answer 2

Hexadecimal is digital number system and it's range from 0 to f.
0-9 and 10-15 = a-f and one hexadecimal entity is represented as 4 binary digits. So widely used color system is rgb or argb, each color will be represented from 0 to 255 in decimal and 0x00 to 0xff in hexadecimal . So each color consists of 8bits, so total ranges for rgb is 24 bits(in hexadecimal is 0x000000 to 0xffffff) and argb is 32 bits (in hexadecimal is 0x00000000 to 0xffffffff)
Example,
RGB:
RED = 0xff0000
GREEN = 0x00ff00
BLUE = 0x0000ff.