I am of the purley personal opinion that most "interrupt" code attempted by people here is totally uneccessary. Interrupts are not a beginners coding exercise. I have done various Arduino projects for a year now, and I still have not found it necessary to use an interrupt. Most of my loop() code is written with a bit care, avoiding blocking code (and certainly never a delay()! ) and usually runs at 10 or 50 Khz (ie takes 100 or 20 microseconds to loop once). See this.
No interrupts, yet this handles serial input, monitors the two switches including software debounce (and some other stuff not used in this proof-of-concept - my first(!) Arduino project)
Declare an unsigned long timervariables for each LED (if you want them to turn on/off at seperate intervals). Repeat the blinkingwithoutdelay code for each of LED, each with its own variables that notes the millis() at start and if the time has elapsed to toggle state.
I wrote another explanation
, it says the same as the short tutorial example, but using a differnet explanation. See if that helps you.