in spells it helps to have a color that means to you so like if you are doing a happiness spell and you use pink because it makes you think of flowers a flowers make you happy but for some people it could mean like love or something.so pink would not bee a good choice in a happiness spell in this situation.it would be better in a love spell.
here is a small color correspondence chart to give you an idea.
red-passion,power,energy
orange-creativity
yellow-positivity
green-trust,peace,money
blue-patience,healing,wisdom
violet-deep understanding