I don't think you really need neither `.` nor `-C`. Just `jq` seems to do the same colored output of the input by default.
`-C` would be required when piping because most of the time (with the exception of piping into less) when stdout is not a terminal, it doesn't make sense to include terminal color escape sequences. You'd end up with those codes in your files, and grep would be looking at them for matches, for example.
`.` would be required when passing the file as an argument instead of stdin, because jq interprets the first argument as jq-code. If you don't include `.` it would interpret the filename as jq-code.
I do honestly think jq is a cool and powerful tool. I also appreciate little things like auto-color when appropriate--git also does this. Git also uses your pager, which might trivialize my personal use case.