There are more United Express aircraft in the new colors because they are new to the fleet. Chautauqua and Shuttle America just joined the United Express family, so their aircraft were repainted right into the new color scheme. Also, some express carriers are receiving brand new aircraft off of the line, so they are being painted with the new colors right away. These aircraft never wore the old blue/gray scheme.
9E, AA, AQ, AX, BA, CO, CP, DH, DL, EV, F9, FL, HA, HP, KL, NK, NW, OH, OO, QX, RP, RW, S5, TW, UA, US, WN, YV, ZK, ZW