236 131 173 255
255 154 108 255
255 224 156 255
244 224 200 255
200 235 125 255
138 178 141 255
143 237 245 255
178 169 231 255
224 143 244 255
DIV:Soft
The first number is the amount of red, the second is the amount of green, and the third is the amount of blue. The fourth number is the transparency. I've had no trouble using this system, and have used it to create a few custom colors.
0 is the minimum value, and 255 is the maximum.
Its really easy to find the values for colors as well. Most programs support RGB values. I happen to use the firefox color picker extension myself, because I can actually pick colors right out of any photo, or off any web page, straight from my browser.