Unforseen logistical issues named as culprit.
SEGA Europe sent out a tweet notifying the delay of the physical release of Sonic Colors Ultimate in the entire EMEA markets. (EMEA stands for Europe, Middle East and Africa.) Citing unforseen logistical issues, without offering a new release date.
The digital release of Sonic Colors Ultimate is not affected by this and will take place on 07-09-2021.