The probability of Grok first drawing a even blue card is \(\frac{3}{7} \cdot \frac{1}{4} = \frac{3}{28}\). The probability of Grok drawing an even red card is \(\frac{4}{7} \cdot \frac{1}{4} = \frac{4}{28} = \frac{1}{7}\). However, he took a card already, so the probability is actually \(\frac{4}{27}\). So, the probability is \(\frac 3 {28} \cdot \frac 4 {27} = \frac 1{63}\)

.