Are painting's name underlined or hyphenated?

Technically, this is a matter of style, not grammar. As such, there
isn't necessarily one specific answer that's right or wrong.  Some
publications will handle it one way, other publications another.

However, by far the most common way for names of paintings to be
treated is to be set in italics.

My main reference on this is the Chicago Manual of Style (section
7.154), 14th Edition, The University of Chicago Press.  This is
considered to be one of the most authoritative sources on matters of
style. Unfortunately, the manual isn't available online.

Other online style guides I have found also say to use italics.  Here
are some examples:

Washington University Publications
http://styleguide.wustl.edu/titles.html

New York University
http://www.nyu.edu/classes/copyXediting/class_style_manual.html

University of Alabama
http://style.ua.edu/esm_t.html

If you do not have the ability to use italics, you may put the name of
the painting in quotes.

University of California at Davis
http://www-styleguide.ucdavis.edu/C.html

I hope this fully answers your question.

Sincerely,

Mvguy-ga





Google search: "style guide" paintings
://www.google.com/search?hl=es&ie=UTF-8&oe=utf-8&q=%22style+guide%22+paintings&btnG=B%C3%BAsqueda+en+Google

Better than expected answer for the price

The name of a painting should be italicized. If italics are not
available, it should be underlined.

"[Italicized]. Titles of published books, plays (of any length), long
poems (usually poems that have been published as books), pamphlets,
periodicals (including newspapers and magazines), works of classical
literature (but not sacred writings), films, radio and television
programs, ballets, operas, instrumental music (but not if identified
simply by form, number and key), paintings, sculpture, and names of
ships and aircraft are all [italicized] in the text."

http://www.carleton.ca/~karmstro/term/MLAHB2_0.htm

"You should include a photocopy of any work of art that you discuss in
your paper. The proper form for this is to cut the photocopied image
out and paste it onto another sheet of paper or to scan the image in
by computer. Under the image you should have the following
information:

- the illustration or figure number that you have assigned it in the
text.

- artist's name, title underlined or italicized (not in quotation
marks), and the date of the work. This information can either be
included in the text at the time you discuss the work or be placed
under the illustration or in a separate list of illustrations at the
end of the paper.

- source of illustration. This resembles footnote form: author, title
of publication, place of publication, date and page or plate number.
If from a periodical, just follow that form."

http://www.presby.edu/writingcenter/guides/art1.html 

I do not understand what your reference to "hyphenated" means in this
sense. If the name of a painting is a compound noun, it might be
hyphenated.

Hello, bakedgoodz,

I think it might help us if you could explain why you think this is a
matter of grammar.  Much depends on why you want to know, how and
where you intend to use the name of any paintings.

Pink's answer is good, as a matter of citation style in an academic
essay or paper, but you will find several other methods used, in text
and on the Internet.  The New York Museum of Modern Art (MOMA) site
does use italics (as at
<http://www.moma.org/collection/depts/paint_sculpt/highlights/index.html>),
while the National Gallery in London prefers quotation marks (as seen
on their current home page at <http://www.nationalgallery.org.uk/> and
throughout their site.

Some sites, especially when using the title as a caption to a copy or
thumbnail of a painting simply use a font size or style which is
different to the name of the artist or other text; at
<http://www.cacr.caltech.edu/~roy/vermeer/ych.html> the painting's
title is in bold, while Global Gallery prefers a smaller font size
<http://www.globalgallery.com/enlarge.asp?print=isi-k716>.

At the Washington National Gallery of Art, you'll see a mix of styles
used, as at <http://www.nga.gov/feature/vermeer/> where the poster
shows a plain style (as opposed to the artist's name in bold), but the
caption below uses italics.

You should also be aware that underlining (a title) in a manuscript or
typescript which is to be printed is an instruction to the printer
that the underlined text should be italicized.  It was commonly used
before word processors became common-place and -scripts were written
by hand or typed on a typewriter which did not have an italic face. 
Don't confuse that type of underlining with hyperlinks, as found on a
web page.  You'll find plenty of instances of italicized  painting
titles which are also underlined - taking you to an illustration of
the painting.

So, much depends on your purpose, the reason you are using the
painting's title, and much depends on the usage expected of you. 
Unless you are writing an academic paper, in which case pink's advice
may hold (possibly dependent on the citation style you are asked to
use), it may be up to you or your institution or organization.  If it
really is up to you, it may not matter whihc style you use - but do be
consistent throughout.

Hope that's helpful, r2l