Hexadecimal Colour Numbers

As you probably know computers know about 0's and 1's. These bits are grouped into bytes - which are 8 bits. Hexadecimal notation was developed as a convenient way of representing bytes. Each dexadecimal has 16 posible values (0 to 15).

In base 10 mathematics 24 is 2x10 + 4.
In base 16 mathematics 24 is 2x16 + 4 (36 decimal).
In base 16 mathematics BC is 11x16 + 12 (188 decimal).

Each 8 bit byte has 256 posible values (0 to 255), which can be represented with two dexadecimals.

Now let's get back to Hexadecimal Colour Numbers, they take the form: "#rrggbb", where rr, gg, and bb are Hexadecimal numbers representing Red, Green and Blue respectively.

For example: "#ffffff" is White, "#ff0000" is Red, "#00ff00" is Green, and "#0000ff" is Blue.

When the colour value is 0 that colour does not contribute to the resulting colour, so black is "#000000". When the colour value is 255 ("ff") the colour is "on full", so "#ff87ff" is Red(256),Green(135) and Blue(255) - which is pink.

The table below can be used to convert to and from Hexadecimal.
The column (C) is placed before the row (R), for example to convert
135 to Hexadecimal, find it in the table... it's in column 8, row 7,
therefore 135 = 87 Hexadecimal.

		C
		0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
R	0	0	16	32	48	64	80	96	112	128	144	160	176	192	208	224	240
	1	1	17	33	49	65	81	97	113	129	145	161	177	193	209	225	241
	2	2	18	34	50	66	82	98	114	130	146	162	178	194	210	226	242
	3	3	19	35	51	67	83	99	115	131	147	163	179	195	211	227	243
	4	4	20	36	52	68	84	100	116	132	148	164	180	196	212	228	244
	5	5	21	37	53	69	85	101	117	133	149	165	181	197	213	229	245
	6	6	22	38	54	70	86	102	118	134	150	166	182	198	214	230	246
	7	7	23	39	55	71	87	103	119	135	151	167	183	199	215	231	247
	8	8	24	40	56	72	88	104	120	136	152	168	184	200	216	232	248
	9	9	25	41	57	73	89	105	121	137	153	169	185	201	217	233	249
	A	10	26	42	58	74	90	106	122	138	154	170	186	202	218	234	250
	B	11	27	43	59	75	91	107	123	139	155	171	187	203	219	235	251
	C	12	28	44	60	76	92	108	124	140	156	172	188	204	220	236	252
	D	13	29	45	61	77	93	109	125	141	157	173	189	205	221	237	253
	E	14	30	46	62	78	94	110	126	142	158	174	190	206	222	238	254
	F	15	31	47	63	79	95	111	127	143	159	175	191	207	223	239	255

Web document by Stephen Peter, S.Peter@unsw.edu.au, last updated 16 Jul 95.