How to reference \paragraph?

Sure - if it has a number which can be referenced:

\documentclass[10pt,twocolumn]{article}
\setcounter{secnumdepth}{6}
\begin{document}
\paragraph{blub}\label{para}
abc paragraph \ref{para}
\end{document}

Here another approach which I find more direct, easy, and appropriate to the question posted above (source: wikibooks):

%The link location will be placed on the line below.
\phantomsection
\label{the_label}

The good thing is that \ref{} will produce the number of the section the paragraph is entailed, \pageref{} will produce the pagenumber where the paragraph is to be found and if hyperlinks are produced automatically with e.g. the hyperref-package clicking on the link beams one to the beginning of the referenced paragraph, ... so correct, consistent, and userfriendly behaviour! :-)

If you use the hyperref and the nameref package and label your paragraph:

\paragraph{The Elephant}\label{para:xyz}

Than you can use \autoref{para:xyz}, \nameref{para:xyz} within your code to get e.g.:

Subsection 3, The Elephant

Obviously I assumed that your paragraph is within subsection 3