Here it is the color chart. Now you can see what colors are assigned to the numbers for the active colors on the halflife models. Look to the left and pick the colors you want your model to have. Then you can type topcolor XXX and/or bottomcolor XXX into the halflife console to change your color. This will let you achieve a wider range of colors than the slides allow in the customize part of halflife. I am showing the colors for the numbers in multiples of ten but some look better at other numbers.

topcolor 230
bottomcolor 70

topcolor 45
bottomcolor 160

topcolor 0
bottomcolor 210