Is there any element that gives off a green tint? A gas?
823492
Chlorine is greenish yellow in gaseous form.  You wouldn't want to use it in your project as it is very poisonous.  \n\nIf you are just going to write about your planet (not build a model) then I suppose you could imagine a planet with a chlorine based atmosphere but unless the laws of chemistry are different in your universe I think the chlorine would react with all sorts of other elements forming solid compounds.  Chlorine wouldn't last long.\n\nIt is possible that your planet's life forms could use chlorine instead of oxygen.  Then the "plants" of that world could replenish its chlorine with a process like photosynthesis.\n\nIf Arthur and Ford visit there they will have to wear space suits to stay alive!\n\nIf you want your atmosphere to glow you could give the planet a strong magnetic field and have it circle a very active sun.  Then there would be auroras in the sky all the time.  That might make it hard for life to get a foothold though.
979836
All elemets will give of colors when excited enough. Some take extremely high energy. Elements can be idntified by these colors. Some elements give off their colors easily, such as the metals in column 1 and 2 and copper. When placed in a flame the outer electrons jump to a higher energy level and when they fall back they fall a specific distance or wavelength. . We see it as the color we perceive.
455657
I have been told it is hail and the sunlight is refracted from  it and thats why it looks green.  The brighter the green the more hail is in the sky
682859
If you could find a gas that had a semi-stable quasistate that when excited would release a photon with a wavelength corresponding to "black", then yes.  However, I don't know exactly what band that would be.  The closest you'd be able to get to black would be a dark ultraviolet, or if you could overlap in phase multiple color lasers which could possibly (but unlikely) add together to make the appearance of black.  Most likely, you're out of luck.
668488
Unleaded fuels-so no lead\nnitrogen compounds come as a result of air combustion in your engine (remember air is approx. 80% Nitrogen).  and you gotta have air to make your engine run.\nSulfur gases can also be a result of this combustion if there is high sulfur content in the fuel. (Shell had a problem with this last year)\nPS. Don't buy into the greenhouse hype, at this point there is NO real evidence either way that fuel combustion makes any difference in the grand scheme of climate dynamics
265731
Carbon dioxide (which is emitted form cars) is the major gas from gases contribute to greenhouse effect, other gases cuase this effect like water vapor, methane, nitrous oxide,and CFC's
928582
A change in color would indicate some sort of reaction.  xenon is a noble gas and is nonreactive, so no.
262227
any oxidative substance (potassium permanganate), ultraviolet rays, sun, air, hydrogen peroxide, etc
78095
Color requires large orbitals to absorb light.  Metal elements are larger than most common non-metal elements, and hence they are more likely to have color than, say, common organic molecules.  However, organic molecules can have conjugated orbitals, which become larger than a single atome and hence are abale to give a coloration in the visible range of the spectrum (as is seen in chlorophyll and carteinoids which color vegetables).  So metal atoms do generally give color, but large molecules with smaller atoms can also make color if the orbitals are conjugated.
1083835
orange and lime green. if not that then lime green
414227
You guys got a lot of it, but the sun is actually green. The atmosphere absorbs much of the light to make it more of a yellowish white light. Pollution and the ozone layer trap and absorb the green light that the sun produces. Then you see what you see. (were you looking at the sun??? :)
460409
Just guess what the colors would be for different compounds before you actually do the flame test for the hypothesis.  \nOr you could guess whether it is the cation (the positively charged metal ion) or the nonmetal anion that is responsible for the different colors.
929317
NO\n\nBlood is red no matter how much oxygen is in it, it just changes to a different shade
570696
It´s 10. Neon. \nIt has two energy levels, filled with 2 and 8 electrons respectively.
166655
Yes, among other gases.  See the link below.
681841
Same principle as neon lighting.  With a neon light you have a gas with current passing through it causing it to emit off a light.  In this case it sounds like a concentration of whatever the specific gas happened to be in the air at the lightning strike, and what you saw was the gas emitting it's light.  Anyone happen to know what gas gives off green light in neon lights?
772787
Indeed, it is the metal. \n\nThe accompanying in is usually NO3 or SO4--Colorless!!\n\n\nGet an "A".