[nigel woods]

I know that most gases are toxic, however I need to insert a gas into a machine safely and then extract it again probably many times over. 
1)  Is there some kind of pellet of solid matter that when mixed with something else will create a coloured gas?
2)  If so how would I apply this and using what apparatus?
3)  Assuming I have now applied my gas how would I extract it and with what apparatus?
The apparatus needs to be rigid and durable not like a hypodermic needle that can break easily and it needs to be able to do that same job many times.
The apparatus needs to be quite small due to the physical extremeties of the machine perhaps 25mm hole or smaller to insert the gas and the gas would need to be quite brightly coloured.
Please also advise places to purchase if you know of any
Any advise would be gratefully appreciated world.
Thanks in advance
nigel@roofframe.co.uk

[Hunter2]

As you said coloured gases are toxic. And there not so many. Chlorine (green) and nitric dioxide NO₂ redbrown colour would be the choices.

Permanganate powder and conc. HCl can develop chlorine gas.  A metall like copper can develop together with conc. nitric acid NO₂ gas.

Or you perchage it in a gas bottle. Companies who sell oxygen, nitrogen, etc. you can asked.

[nigel woods]

As you said coloured gases are toxic. And there not so many. Chlorine (green) and nitric dioxide NO₂ redbrown colour would be the choices.

Permanganate powder and conc. HCl can develop chlorine gas.  A metall like copper can develop together with conc. nitric acid NO₂ gas.

Or you perchage it in a gas bottle. Companies who sell oxygen, nitrogen, etc. you can asked.

I am a complete idiot in this field - please give me the laymans terms

1) Are there any other colours other than green and redbrown which can be obtained?
2) If I obtainconc nitric acid and a small bit of copper, will the copper completely disolve?
3) How should I mix these - in a test tube or something else?
4) Will nitric acid be corrosive to anything other than glass ie can I put it in a plastic container or not?
4a) How much copper and nitric acid do I need for a gas to fill approx 0.053m3 area.
4b) How do I extract the gas completely afterwards?  Is there another compound / solid / product that I can add (or expose to the gas) that will dissipate the gas?
5) If I used the Permanganate powder and conc. HCl (I dont understand what this HCl is or means - is it a liquid or solid) that can develop into a chlorine gas, what should i mix and blend them together in?  And also how do I extract them afterwards so that the gas has done completely?  Again Is there another compound / solid / product that I can add (or expose to the gas) that will dissipate the gas?
Sorry to sound foolish but I have never done any chemistry before so a laymans explanation would be better for me to comprehend and undertake.
Many Thanks

[Arkcon]

I think from a purely mechanical basis, your idea is flawed.  There are a number of gasses that are colored, although the commonly known ones are toxic.  You could also used dyed smokes, of which there are many commercial versions.  But when you want to insert and extract it, many times over, and I assume, you want to leave none behind when you extract, I think you may be expecting too much.  Maybe in a smooth glass tube, vented to disperse the gas, would work.  But a syringe-type device won't pull and push a gas that smoothly.

Somebody once wanted to use science to make their own Remembrall -- http://www.chemicalforums.com/index.php?topic=30320.0  and that just isn't practical

[fledarmus]

This process is typically done with electrical energy rather than gases - many otherwise colorless gases glow when a current is applied. Noble gases are especially useful in this regard, and are used to make neon lights, krypton lights, and xenon lights. Sodium vapor and mercury vapor also glow brightly in the presence of a current.

As you mentioned that you are not a chemist, you might like some thoughts on the colored gases that have been proposed. Chlorine gas is quite toxic, as is nitrogen dioxide. Both dissolve and react rapidly in water to form strong acids, hydrochloric acid (HCl) from chlorine gas and nitric and nitrous acid from nitrogen dioxide. (This reaction occurs in the lungs and mucuous membranes, which gives rise to their high toxicity, as well as in the atmosphere, making them very corrosive to everything in the area). Both are strongly corrosive, especially if traces of water are available. Chlorine is a very pale color and probably not strongly colored enough for your purposes anyway. Bromine is much stronger colored, but even worse as far as toxicity and corrosion goes.

Depending on your application, Arkcon's colored smoke suggestion might be more helpful. Tiny pyrotechnic charges can produce the smoke, with a compressed gas system to vent it afterwards. I don't know your application, but I am envisioning a small Y-shaped tube with the smoke charge in one arm, compressed air, CO₂, or nitrogen in one arm, and an outlet in the third. The charge would fill the tube with smoke, and a blast of compressed gas would clear it again.