There's red= fire, blue= water, yellow= electric, green= grass. The confusing part may be gold and yellow, you can tell something is gold by the darker sections inside the card such as here:
compared to yellow:
other than that there's diamond which should be different enough.
Then there's radiant versions of the 4 creatures, infurno has a blue fire, zappit is yellow instead of orange, walle is pink instead of blue and wrackoo is purple instead of green.
Ok, so the foils only apply to the creature cards. That makes sense
yes but also empty cards!