Helium itself is colorless, odorless, and tasteless - a true invisible gas. You can't see it, smell it, or taste it.

However, you can observe its effects. For example, you can see the balloons inflate when filled with helium, or see the lighter-than-air balloons float. You can also hear the high-pitched sound of helium when it's inhaled (though this is not recommended).

But helium itself is simply an invisible gas, just like air.