Glowing two leds alternatively in a given ratio of time
I'm not going to give you the whole circuit, but here's something to get you started.

There are hundreds of 555 astable timer circuits on the net, here are a few.  You can compute the resistor and capacitor values for your circuit using a calculator like the one here which lets you input a duty cycle.

Pick values of C, RA and RB (also labeled C, R1 and R2) such that the capacitor and one of the resistors are the same for the two duty cycles you want, and only one resistor needs to change value.  Then use the circuit below to dynamically change the resistor value based on the input voltage:



The reference voltage of 5V for the comparator assumes a supply voltage of 12V; adjust as needed.  Use a voltage reference if you need something more precise.  When the input voltage is greater than 5V, R3 is selected into the circuit; otherwise R4 is used.

The analog switch will have some internal resistance, so you will need to subtract that from the calculated values to get the required values of R3 and R4.