Rewriting a variable in a querystring with .htaccess

Question

I use a PHP script with my site that produces a querystring in the URL. One of the variables in the querystring is: colour=red

I would like to make a rule i

Answer 1

RewriteEngine On
RewriteCond %{QUERY_STRING} ^(.*&|)colour=red(&.*|)$  # search colour=red
RewriteRule ^(.*)$ $1?%1colour=blue%2 [L,R=301]       # redirect to colour=blue

This will redirect URLs with colour=red in query-string to URLs with colour=blue