Do you have an external monitor hooked up? The screen flashes blue on Macs primarily when the system is reconfiguring the screens -- e.g. if you plug in an external display, the internal display will also flash blue while the system gets reconfigured to do screen spanning. Normally, at least on Macs I've used, the screen goes from black to the normal desktop when you wake from sleep without a blue screen, if you don't have external displays plugged in.
But as stated above, if you have a kernel panic, you'll know. You'll definitely know.