Question

Neon's gross color was orange. Individual spectral lines had colors ROY G BI.

Krypton's gross color was a whitish purple. Individual spectral lines had colors O G IV.

Xenon's gross color was white with a hint of blue. Individual spectral lines had colors ROY G BIV.

How do the gross colors of the gas tubes compare to the individual spectral lines? Does the gross color result from a combination of spectral lines or one intense line?

Answer 1

An interesting question. Let us have a perspective. Individual spectral lines are a product of the interaction between an entity like an atom and light (basically its smallest unit photon). The number of spectral lines corresponds to the number of such "distinct" interactions. So your question if the gross colour arises out of a combination of spectral lines or one intense line holds.  

I believe it is due to the combination of spectral lines and their intensities. Take the example of sunlight, it appears white because it comprises the VIBGYOR. And the resultant of this combination is white. So Neon tubes appearing orange, Krypton whitish purple may be due to the resultant colour produced from the individual spectral lines.

Also if we consider colour complementarity, we know that if two colours are complementary and are present in a certain proportion, they produce a neutral colour. The complementary colour of Red is Green, Blue is Orange, Yellow is Purple. This might explain why the resulting colours are the way there are.