No, not usually with the naked eye.
You can see some halogen gases, such as Chlorine and Bromine and Iodine because they are coloured. Most other gases are colourless and cannot be seen.
Almost all of the principal gases in the atmosphere are colourless. Hence we see the air as colourless.
Something you mite want to see is all the gases and maybe collect a sample
all of them are because they are all gases
The Short Answer is Yes. We see all around Us that the Long Answer is also Yes.
Eventually all body systems will see the effects of dangerous gases, but the most immediate effects will be seen by the respiratory systems and the circulatory systems.
By tinting them.
Yes, all ladybugs expel gases. All living things expel gases.
No, In fact nearly all gases won't contain it, for example all gases on the periodic table won't contain it
No, not all gases have a distinct smell. Some gases are odorless and cannot be detected by smell alone.
1) they are all gases 2) they are all monoatomic
the noble gases would be the lightest, as they are all gases