[NTG-context] Quotations

I use \startquotation and \stopquotation a lot. I would like to visually strengthen the quotations because some are pretty lengthy and a reader might forget that it is not me that is writing here. I have been thinking about applying a light grey background or a border of sorts (which should then be open at the top of bottom if the quotation flows over a page boundary. Can someone tell me how to do this? Thanks, G