how can u save a color u've created on photoshop cs 8.0?

Answer 1

You can make a small bitmap file (swatch) with the color so you can sample it whenever you want to or you can remember the RGB or Hex value.
I usually just write down the Red Green Blue Hex Value.
For example pure Red is #FF0000

Answer 2

Get your colour using the colour picker or whatever. On the top bar, go to Window > Swatches.

On the Swatch menu simply press the "Create New Swatch from Selection" icon. It should look like a little square with a folded corner.