You can be sure that if they could paint, they could talk.
How can you be so sure though? None of us can unless we find writing they left behind instead of piccies!
But I dont entirely doubt you after reading this:
Quick quote in that link:
"The discovery of the gene, called FOXP2, have provided the strongest evidence yet that these heavily built species were capable of speech, although the researchers are unable to say what extent their linguistic ability would have been.
FOXP2 is thought to be crucial to the development of language as it governs the fine control of muscles that is needed to form words with the larynx, lips and tongue".
And further down that page
"But some scientists have warned that it is not possible draw any conclusions about the Neanderthals ability to speak from the research, which is published in the journal Current Biology".
You say: You can be sure that if they could paint, they could talk"
And long before both my sons were talking ...they both did their finger paintings... and of that I am indeed sure!