Download it here (you need the multiplayer version)
Bullseyecrosshairs.com
and replace Halflife2.ttf in the mod's Resource folder.
The color is customized in ClientScheme.res file in the same folder.
Color is set in the line that reads
Normal: 0 255 255 255 (zero for red, maximum for green, blue and opacity)
Crosshair color's Additive property is to be set to 0 (otherwise it will be white on lighted white backgrounds).
Check out this crosshair in HD View :)