grep: unrecognized option `--color'

gitのgrepを呼んでいるようだ。

$ grep -v
grep: unrecognized option `--color'
Usage: grep [OPTION]... PATTERN [FILE]...
Try `grep --help' for more information.

$ where grep
d:\Users\m_fujii\AppData\Local\Atlassian\SourceTree\git_local\bin\grep.exe
d:\cygwin64\bin\grep.exe