oh, sorry, I don't konw Wolfgang has replied to this question. Please take the method provided by Wolfgang.
 
From: timli2013@outlook.com
To: ntg-context@ntg.nl
Subject: RE: [NTG-context] [***SPAM***] Changing the font of the TOC-Title
Date: Mon, 15 Apr 2013 08:20:11 +0000

I have achieved this by the following method:

 I think we'd better only change the label by \setupheadtext and chage its style by \setuphead. An example as follows
 
\setupheadtext[content={CONTENTS}]
\def\mytitle#1{%
  \midaligned{#1}}
\setuphead
  [title]
  [style={\bfb},
   color=red,
   before={},
   after={\blank[3*big]},
   textcommand={\mytitle}]
 
it works well for me :-)
 
but please note that if you use \title in the frontmatter, the title also will be changed. Maybe you want to define your own title to solve this problem.
> Date: Mon, 15 Apr 2013 08:06:54 +0200
> From: h.oezoguz@mmnetz.de
> To: ntg-context@ntg.nl
> Subject: [NTG-context] [***SPAM***] Changing the font of the TOC-Title
>
> Hello,
>
> I know, that I can change the TOC-Title by
>
> \setupheadtext[content=Whatever the TOC-Title may be]
>
> How can I change the Font of the TOC-Title, is there a style key, or
> somewhat like that?
> (Directly "\setupheadtext[content=Whatever the TOC-Title may be,
> style=Chapterstyle]" does not work, where "Chapterstyle" is a defined Font)
>
> Huseyin
>
>
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