Here's what the Orbs CCG rules say:
"Once per turn, you may discard any card for one energy of its color. This is called converting the card into energy. Multicolored cards are converted into one generic (gray) energy.
You must pay a card's energy cost in order to play it. Fortunately, generic (gray) energy costs can be paid with any type of energy, not just generic energy. Colored energy costs, however, requires colored energy.
For example, if you have 1 green and 1 red energy, you can play a card that costs 1 green and 1 generic energy, but not a card that costs 2 green energy.
Your energy regenerates at the beginning of each turn. For example, if during each your first two turns you discarded a yellow card for energy, then you will have two yellow energy at the beginning of your third turn (and all subsequent turns). As the game progresses, you'll be able to afford more powerful cards.