Lighthouse solution from top to bottom ...

Yellow = #2
Orange = #7
Blue = #4
Purple = #6


Procedure:

Step 1: Set Yellow to #2

Step 2 Set Orange to #7: To do this see the number on the Orange dial and remember how many more turns is needed to make it #7. Go down a level and turn the Blue dial the number of turns required to make Orange #7. Check Orange is set to #7.

Now Yellow and Orange are set to their correct numbers but more importantly they are in sync with eachother.

Step 3 Sync Blue and Purple: In this step we need to set the Blue dial to two number lower than whatever the Purple dial currently reads. We need to do this step using the Orange dial. When turning the Orange dial it moves the Blue dial and the Yellow dial; all the while keeping Orange and Yellow in sync with eachother.
Now go and see what the numbers on the Purple and Blue dials are. Go to the Orange dial and turn the Orange dial the number of turns required to set the Blue number two numbers lower than what the number the Purple dial reads.
e.g. if the Purple dial is #5 we want to turn the Orange dial which turns the Blue dial at the same time until the Blue dial is set to #3.
Check that the Blue number is two numbers lower than the Purple number.

Now Yellow and Orange are still in sync with eachother because we turned the Orange dial. The Blue and Purple are now in sync with eachother as well.

Step 4: Set Purple to #6 this will set Blue to #4 (since we set Blue up so that it was two numbers behind Purple in the last step).

Step 5: Set Yellow to #2 this will automatically set orange to #7.

There you have it Yellow = #2, Orange = #7, Blue = #4, Purple = #6

Too easy? I think so! 8)

... now on to the radios and the rest of the easter egg ...