Color palette table with color numbers listed. The current version of ldconfig.ldr containing the definitions for these colors can be found here [4]
Tables with all RGB values, color names, number and properties have been set up at these pages:
Having the following characteristics:
Solid colors

List of embedded colors in official parts:
0 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 16 19 23 24 25 32 33 36 39 40 46 47 256 257 258 260 263 264 270 276 295 300 320 326 334 353 354 358 366 370 374 382 383 391 430 431 462 485 486 487 495 496 503
List of embedded colors in official parts as well as parts on the PT
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 19 23 24 25 27 32 33 34 36 39 40 41 42 46 47 57 70 71 72 79 151 256 257 258 260 263 264 270 272 276 288 295 300 320 326 334 353 354 358 366 370 374 375 378 382 383 391 430 431 450 462 478 484 485 486 487 494 496 495 496 503
List of colors used in PT parts but not official parts
11 27 34 41 42 57 70 71 72 79 151 272 288 375 378 450 478 484 494 496
Useful links
LDraw.org Colour Definition Language Extension: http://www.ldraw.org/Article299.html [9]
LDraw.org Color Chart: http://www.ldraw.org/Article93.html [10]
Official LEGO Color Chart at Peeron: http://www.peeron.com/cgi-bin/invcgis/colorguide.cgi [11]
Peeron.com Color Chart: http://www.peeron.com/inv/colors [12]
Bricklink.com Color Chart: http://www.bricklink.com/catalogColors.asp?v=0&itemType=P&itemNo= [13]
Clark Stevens' Color Chart: http://www.isodomos.com/ColorTree [14]
Scott's Color Manager to bake a MLCad.cfg file: http://www.scottwardlaw.com/colormanager/ [15]