Formatting applied via Find Replace always applies to the entire found string.

FWIW, your Find/Replace expression could be reduced to (for example):
Find = (: )(*^13)
Replace = \1\2
Regardless, formatting the space after the colon as bold seems rather pointless. I would suggest two Find/Replace operations
Find = : (*^13)
Replace = §\1
replacement = bold
Find = §
Replace = :^32
replacement = not bold

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]