311 bytes added
, 14:20, 9 January 2014
The default Index for ConTeXt groups words under lowercase headings.
To change these to uppercas bold headings, use the following setting near the top of your document.
\setupregister[index][style=\bold\Word]
Thanks to mpfusion for this answer that he gave me in the IRC chatroom at /server irc.freenode.net .