Backticks do capture the raw output, but on most systems grep is configured to omit the ANSI color codes when it writes to a pipe (and not to a terminal) via the option --color=auto.

You check by simply writing

$ echo foo | grep foo   # output in read on my terminal
foo
$ echo foo | grep foo | cat # output in grey on my terminal
foo
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Use --color=always to force color codes.