Simultaneously generate 3 output signals

Hi , i have an arduino uno R3. I m trying to generate inside the main loop, 3 different "signals"(output) as :

-one signal to light a red led once every 250 ms; -one signal to light a blue led once every 500 ms; -one signal to light a green led once every 1 seconds;

Could you please help me figure out how can i do this ? I think i need inside the main loop, 3 other loops, which should work simultaneously.

Thanks in advance!

How do you imagine lights working “simultaneously” if they blink for different periods of time?

To set port pins simultaneously, use direct digital output, for example.

PORTD = 0xFF; //set all output bits of PORTD to 1

Thanks @jremington, but

I don't know if i was clear enough, i want to see 3 leds , each blinking at it's own frequency

See the tutorial "How to do several things at once".

thanks a lot Sir!!!!