How to flash between two different sets on LEDs using a 556 Timer IC
Here's a circuit that uses the constrained component set and performs (more-or-less) the requested function. Because of the way the 555 works, the first toggle is about 80 seconds in, and the following transitions follow every 30 seconds with the given components. 



The components in the box on the left simulate a pushbutton conected from E to C on Q1 that is pressed 70ms after the 6VDC power V1 is applied. 

Simulation works fine in LTSpice, though the 555 is a CMOS type (despite being called an LM555). 

Q1 and Q2 perform the latching power switch from the momentary pushbutton. C3 is a bypass capacitor. C1 and R1 are the timing components, ideally C1 will be a low leakage +/-10% type such as Nichicon UKL series, however in practice just about any normal radial lead non-low-impedance standard electrolytic will work fine. 

The 555 switches the LED D1 directly, and the network D3/R7/R5 is necessary because the output voltage can be quite high when sinking significant current, and we wish Q4 to remain off when D1 is on (output low) so either D1 or D2 is on at all times when the switched supply voltage is present. 



Contrast this with using a microcontroller such as the 8-pin PIC12F675 operating from 4.5V. 

Aside from the switch and LEDs, you would need only the microcontroller, one or two resistors and a 100nF bypass capacitor.