Hi @rebecca28,
I’m with you and Megan - it’s always smart to work through any potential mundane explanations. If you’d eliminated any potential colorings/chemical intervention, then it’s worth exploring some potential magickal explanations too! 
In magick, there are a few ways to interpret a strong, bright, and big flame:
You could also consider the magickal properties of the color green:
Green
The meaning of the color green is vast and varied. In some cultures, it is associated with nature and the environmentally friendly movement. For others, it represents wealth, fertility, and abundance. And still for others, green is the color of healing and renewal.
It’s no surprise that the color green is often used spells as a way to manifest our intentions. Whether we are seeking financial abundance or physical healing, the color green can help us to connect with those energies. When used in combination with visualization and other positive affirmations, a green candle can be a powerful tool for witchcraft and manifestation.
Sometimes even when They aren’t actively called upon, deities or guiding spirits can make Themselves known.
I know you said you weren’t working with anyone in specific for this spell, but are there any deities you currently work with (or feel called to) in general? That could be worth exploring as well!
Whatever you choose to do from here, wishing you all the best with your casting - blessed be, Rebecca! 
