Are there colors humans can't see?

Red-green and yellow-blue are the so-called "forbidden colors." Composed of pairs of hues whose light frequencies automatically cancel each other out in the human eye, they're supposed to be impossible to see simultaneously. By some estimates, they can see about 100 million different colors or about 99 million more than we can! This is due largely to the fact that many tetrachromats have a fourth cone sensitive to the ultraviolet part of the spectrum, which is invisible to the human eye. Blue is the hardest color to see as more light energy is required for a full response from blue-violet cones.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.