First of all you need to know that An element is known for the no. of protons in the nuclei .
Different no. of protons means different elements.
say you have Hydrogen atom , you increased proton , it will become helium ion (as you didn't increased electrons in it , it can't be neutral )
1 proton + 1 electron (Hydrogen) ---> 2 proton + 1 electron (Helium+) .
But the problem is that every configuration of nucleus (isotopes) is not stable .
Helium has 5 observed isotopes .
Helium-2 --> 2 proton + 0 neutron ( which we made in above example) - it is the most unstable isotope of helium .
Helium-3 --> 2 proton + 1 neutron
Helium-4 --> 2 proton + 2 neutron -( most of the time we refer to this isotope when we talk about Helium.) - most abundant isotope of helium
Helium-5 --> 2 proton + 3 neutron
Helium-6 --> 2 proton + 4 neutron
Actually all of isotopes of a element almost have same chemical properties i.e they will react similarly .
but they are different in case of density , boiling point.
There color is almost identical (you can't observe it by your eyes , you need a really good instrument to observe it )
So logically if you added 1 proton to Gold it will became Mercury .
gold is yellowish while mercury is silvery.