The effect can be turned off and on by removing/placing the ':' in 'file:' in the second xml-line.

Is this a bug? It certainly is annoying that the default color is inadvertently changed.

A (somewhat) minimal example follows:

===================================================================

\setupcolors[state=start]

\definecolor [mistyrose] [r=1,g=.894118,b=.882353]

% Setup coloring for framed text (unbreakable) blocks.

\defineframedtext[framedcode][frame=on,corner=round,rulethickness=2pt,

width=\textwidth,color=codecolor,style=\ttxx,

background=color,backgroundcolor=mistyrose,framecolor=indianred]

% Setup coloring for verbatim code fragments.

\definecolor [codecolor] [red]

\definecolor [colorprettyone]   [codecolor]

\definecolor [colorprettytwo]   [codecolor]

\definecolor [colorprettythree] [codecolor]

\definecolor [colorprettyfour]  [codecolor]

\setuptyping [color=codecolor,palet=colorpretty]

% XML typesetting inside framebox with background.

\definetyping[XMLBOX][option=XML,style=\ttxx,

before={\bgroup\setupinterlinespace[line=2ex]\startframedcode},

after={\stopframedcode\egroup}]

\starttext

Testing xml typing\crlf

\startXMLBOX

<?xml version="1.0" encoding="UTF-8"?>

<locationURI>zip:/?file////path/to/a.zip</locationURI>

\stopXMLBOX

This color is black as it should be.

\startXMLBOX

<?xml version="1.0" encoding="UTF-8"?>

<locationURI>zip:/?file:////path/to/a.zip</locationURI>

\stopXMLBOX

This color should be black not \quote{codecolor}!!!

\stoptext