Q. I can’t find any reference in CMOS 16 to how odds should be punctuated.
A. Odds are ratios. Ratios may be expressed in numerals with a colon and no spaces or with numbers spelled out or not according to the guidelines in chapter 9:
The odds are 451:1.
The odds are 3:2.
The odds are 451 to 1.
The odds are three to two.
[Update: CMOS 17 covers this in paragraph 9.58.]