The point of UDL/UDI (universal design for learning / universal design of instruction) is simply to make every part of what you do transparent and legible to the broadest range of students. This is a good beginning place for UDI; it includes a bibliography with several things I referenced in our meeting.

Several universities have especially good centers for teaching and learning with online resources about diversity. Arizona and Michigan are among the best. 

This 1997 report is cited everywhere as the origin argument for diversity initiatives at campuses across the country; this 2000 report reflects on classroom impacts in particular.

This is a now-classic 2002 article from Harvard Educational Review that is a good beginning spot for colleagues new to the conversation about why diversity in the classroom matters. 

Culturally Responsive Teaching: Theory, Research, and Practice, now in its third edition, is a good assemblage of a lot of research with accompanying practical suggestions concluding every chapter. It’s not all relevant for the college classroom, but it is nonetheless a good place to start.

This text, produced by the Derek Bok Center at Harvard, has good advice for conflict moments in the classroom.