I can only verify this works under a series 6 motherboard. Go into the BIOS, look under Power Settings, System Power Options. There is a setting called "S3 State Indicator". Set it to off. That should do what you want.
Thanks Brad, this indeed does exactly what I wanted so I'm perfectly happy now (well, except for the part where I feel stupid for totally failing to find this very reasonably named option myself somehow :-)
Alternative option is to replace the 1 color led with a two color led, but that would be a hardware modification as most cases ship with a 1 color power led. It is not to difficult to replace the power led however.
I also found the blinking annoying. In other systems the led goes gently on/off when the system is in sleep mode. I cannot image that creating such a circuit would be difficult for Intel..