Caught Mid-Switch

A status LED cycles through three colours in order: blue for 50 seconds, then amber for 5 seconds, then green for 45 seconds, then back to blue, repeating forever.

A technician watches the LED for exactly 5 seconds, starting at a uniformly random moment of the cycle. What is the probability that she sees the LED change colour at some moment during her 5-second glance? Give an exact fraction.