Consider the rainbow.  Everyone sees something different when looking at a rainbow
A physicist sees a practical demonstration of the refraction of light across the visible spectrum.
An Old Testament scholar sees a reminder of the covenant G-d made with Noah.
A New Testament scholar sees a reminder of the fulfillment of the promise of a Deliverer.
A child sees pretty colors.
A storyteller sees a leprechaun protecting his pot of gold.
An artist sees brilliant hues and gorgeous transitions.
A meteorologist sees the end of a long rain.
All of them are looking at the same rainbow.  It is objectively measurable.  Everyone sees the same thing.  We all agree what we are seeing, hearing, etc.  We agree on the shape, color, size, location and so on.  The rainbow as an object does not vary.  The interpretations men make of it, when seeing it as a symbol, however, will.
Masonry shows us rainbows, and asks us to consider what they mean, what we see in them.  Different people will see different things in the same rainbow.