Same issue with out of bounds warning - I could dismiss the warning and then hit the print button again to get it going.
There also is a check box in OctoPrint that controls this behavior, and if I recall it is labeled as a beta feature. I unchecked and the warning went away.
I created two profiles in S3D, one for dual color, and the other for a single color. The single color was a copy of a FT5 with changes for print dimensions. My dual color profile was generated from single color profile, and then I used the built in assistant (Dual Extrusion Wizard) for two color.
I followed this and the first 2 color print amazingly worked: