Number 12- Clint Barmes
Clint Barmes wore the number 12 from 2003 through 2006 and again from 2008 through 2010. In 2007, he mainly spent the season in Triple-A Colorado Springs as he only played 27 games at the MLB level.
With the Rockies overall, he played to a 9.3 bWAR but if you exclude 2007, it actually goes up to 9.6. The next closest guys who wore the number and played multiple seasons with the Rockies are Mark Reynolds (3.0 bWAR) and Mike Kingery (1.5 bWAR).
Number 13- Charlie Hayes
Number 13 is another that has often been worn by coaches as Clint Hurdle wore the number from 1997 through 2003 as first base coach/hitting coach and manager and from 2005 until his firing in 2009 (veteran pitcher Jeff Fassero wore it in 2004 and Hurdle flipped his number and went to 31).
Before Hurdle came along, Charlie Hayes wore it and he is still the best player to wear it for the Rockies. In his two seasons as a Rockie (1993-94), he hit .298/.352/.484 with an OPS+ of 106 and a bWAR of 4.1 in 270 games.