Pour choisir un code couleur, il faut savoir comment ils fonctionnent. Très simplement, c'est une suite de nombres qui donnent la composition en rouge, vert, bleu.

Un petit lien pratique vers un site listant toutes les couleurs possibles sur le web

Voici la table des couleurs les plus utilisées fourni par Francisek:

Palette standard des 216 couleurs Web Avec codes HTML et composantes rgb
#000000 (0,0,0)	#000033 (0,0,51)	#000066 (0,0,102)	#000099 (0,0,153)	#0000CC (0,0,204)	#0000FF (0,0,255)
#003300 (0,51,0)	#003333 (0,51,51)	#003366 (0,51,102)	#003399 (0,51,153)	#0033CC (0,51,204)	#0033FF (0,51,255)
#006600 (0,102,0)	#006633 (0,102,51)	#006666 (0,102,102)	#006699 (0,102,153)	#0066CC (0,102,204)	#0066FF (0,102,255)
#009900 (0,153,0)	#009933 (0,153,51)	#009966 (0,153,102)	#009999 (0,153,153)	#0099CC (0,153,204)	#0099FF (0,153,255)
#00CC00 (0,204,0)	#00CC33 (0,204,51)	#00CC66 (0,204,102)	#00CC99 (0,204,153)	#00CCCC (0,204,204)	#00CCFF (0,204,255)
#00FF00 (0,255,0)	#00FF33 (0,255,51)	#00FF66 (0,255,102)	#00FF99 (0,255,153)	#00FFCC (0,255,204)	#00FFFF (0,255,255)
#330000 (51,0,0)	#330033 (51,0,51)	#330066 (51,0,102)	#330099 (51,0,153)	#3300CC (51,0,204)	#3300FF (51,0,255)
#333300 (51,51,0)	#333333 (51,51,51)	#333366 (51,51,102)	#333399 (51,51,153)	#3333CC (51,51,204)	#3333FF (51,51,255)
#336600 (51,102,0)	#336633 (51,102,51)	#336666 (51,102,102)	#336699 (51,102,153)	#3366CC (51,102,204)	#3366FF (51,102,255)
#339900 (51,153,0)	#339933 (51,153,51)	#339966 (51,153,102)	#339999 (51,153,153)	#3399CC (51,153,204)	#3399FF (51,153,255)
#33CC00 (51,204,0)	#33CC33 (51,204,51)	#33CC66 (51,204,102)	#33CC99 (51,204,153)	#33CCCC (51,204,204)	#33CCFF (51,204,255)
#33FF00 (51,255,0)	#33FF33 (51,255,51)	#33FF66 (51,255,102)	#33FF99 (51,255,153)	#33FFCC (51,255,204)	#33FFFF (51,255,255)
#660000 (102,0,0)	#660033 (102,0,51)	#660066 (102,0,102)	#660099 (102,0,153)	#6600CC (102,0,204)	#6600FF (102,0,255)
#663300 (102,51,0)	#663333 (102,51,51)	#663366 (102,51,102)	#663399 (102,51,153)	#6633CC (102,51,204)	#6633FF (102,51,255)
#666600 (102,102,0)	#666633 (102,102,51)	#666666 (102,102,102)	#666699 (102,102,153)	#6666CC (102,102,204)	#6666FF (102,102,255)
#669900 (102,153,0)	#669933 (102,153,51)	#669966 (102,153,102)	#669999 (102,153,153)	#6699CC (102,153,204)	#6699FF (102,153,255)
#66CC00 (102,204,0)	#66CC33 (102,204,51)	#66CC66 (102,204,102)	#66CC99 (102,204,153)	#66CCCC (102,204,204)	#66CCFF (102,204,255)
#66FF00 (102,255,0)	#66FF33 (102,255,51)	#66FF66 (102,255,102)	#66FF99 (102,255,153)	#66FFCC (102,255,204)	#66FFFF (102,255,255)
#990000 (153,0,0)	#990033 (153,0,51)	#990066 (153,0,102)	#990099 (153,0,153)	#9900CC (153,0,204)	#9900FF (153,0,255)
#993300 (153,51,0)	#993333 (153,51,51)	#993366 (153,51,102)	#993399 (153,51,153)	#9933CC (153,51,204)	#9933FF (153,51,255)
#996600 (153,102,0)	#996633 (153,102,51)	#996666 (153,102,102)	#996699 (153,102,153)	#9966CC (153,102,204)	#9966FF (153,102,255)
#999900 (153,153,0)	#999933 (153,153,51)	#999966 (153,153,102)	#999999 (153,153,153)	#9999CC (153,153,204)	#9999FF (153,153,255)
#99CC00 (153,204,0)	#99CC33 (153,204,51)	#99CC66 (153,204,102)	#99CC99 (153,204,153)	#99CCCC (153,204,204)	#99CCFF (153,204,255)
#99FF00 (153,255,0)	#99FF33 (153,255,51)	#99FF66 (153,255,102)	#99FF99 (153,255,153)	#99FFCC (153,255,204)	#99FFFF (153,255,255)
#CC0000 (204,0,0)	#CC0033 (204,0,51)	#CC0066 (204,0,102)	#CC0099 (204,0,153)	#CC00CC (204,0,204)	#CC00FF (204,0,255)
#CC3300 (204,51,0)	#CC3333 (204,51,51)	#CC3366 (204,51,102)	#CC3399 (204,51,153)	#CC33CC (204,51,204)	#CC33FF (204,51,255)
#CC6600 (204,102,0)	#CC6633 (204,102,51)	#CC6666 (204,102,102)	#CC6699 (204,102,153)	#CC66CC (204,102,204)	#CC66FF (204,102,255)
#CC9900 (204,153,0)	#CC9933 (204,153,51)	#CC9966 (204,153,102)	#CC9999 (204,153,153)	#CC99CC (204,153,204)	#CC99FF (204,153,255)
#CCCC00 (204,204,0)	#CCCC33 (204,204,51)	#CCCC66 (204,204,102)	#CCCC99 (204,204,153)	#CCCCCC (204,204,204)	#CCCCFF (204,204,255)
#CCFF00 (204,255,0)	#CCFF33 (204,255,51)	#CCFF66 (204,255,102)	#CCFF99 (204,255,153)	#CCFFCC (204,255,204)	#CCFFFF (204,255,255)
#FF0000 (255,0,0)	#FF0033 (255,0,51)	#FF0066 (255,0,102)	#FF0099 (255,0,153)	#FF00CC (255,0,204)	#FF00FF (255,0,255)
#FF3300 (255,51,0)	#FF3333 (255,51,51)	#FF3366 (255,51,102)	#FF3399 (255,51,153)	#FF33CC (255,51,204)	#FF33FF (255,51,255)
#FF6600 (255,102,0)	#FF6633 (255,102,51)	#FF6666 (255,102,102)	#FF6699 (255,102,153)	#FF66CC (255,102,204)	#FF66FF (255,102,255)
#FF9900 (255,153,0)	#FF9933 (255,153,51)	#FF9966 (255,153,102)	#FF9999 (255,153,153)	#FF99CC (255,153,204)	#FF99FF (255,153,255)
#FFCC00 (255,204,0)	#FFCC33 (255,204,51)	#FFCC66 (255,204,102)	#FFCC99 (255,204,153)	#FFCCCC (255,204,204)	#FFCCFF (255,204,255)
#FFFF00 (255,255,0)	#FFFF33 (255,255,51)	#FFFF66 (255,255,102)	#FFFF99 (255,255,153)	#FFFFCC (255,255,204)	#FFFFFF (255,255,255)

Note: Pour trouver des couleurs qui vont bien ensemble:
Francisek a pondu un outil très pratique: http://francisek.over-blog.com/article-151196.html