To determine what tier is your card, take note of the title color of your card.
T1 simply means Tier 1 and so on.
Now what about the colors? OK let's say I have here two cards with the same title name but with different colors. The first card is a white one and second card is purple one. Assuming the first card which is a common card has a "Ready" of 6, the second card which is an epic card will have a "Ready" of 4.