RewriteEngine On
RewriteLogLevel 3
RewriteRule ^/function/([^:/]+):([^:/]+)$ /function?$1=$2 [L,QSA]
RewriteRule ^/function/([^:/]+):([^:/]+)(/.+)$ /function$3?$1=$2 [N,QSA]

で、

(2) init rewrite engine with requested uri /function/aaa:1111/bbb:2222/ccc:333
(3) applying pattern '^/function/([^:/]+):([^:/]+)$' to uri '/function/aaa:1111/bbb:2222/ccc:333'
(3) applying pattern '^/function/([^:/]+):([^:/]+)(/.+)$' to uri '/function/aaa:1111/bbb:2222/ccc:333'
(2) rewrite '/function/aaa:1111/bbb:2222/ccc:333' -> '/function/bbb:2222/ccc:333?aaa=1111'
(3) split uri=/function/bbb:2222/ccc:333?aaa=1111 -> uri=/function/bbb:2222/ccc:333, args=aaa=1111
(3) applying pattern '^/function/([^:/]+):([^:/]+)$' to uri '/function/bbb:2222/ccc:333'
(3) applying pattern '^/function/([^:/]+):([^:/]+)(/.+)$' to uri '/function/bbb:2222/ccc:333'
(2) rewrite '/function/bbb:2222/ccc:333' -> '/function/ccc:333?bbb=2222'
(3) split uri=/function/ccc:333?bbb=2222 -> uri=/function/ccc:333, args=bbb=2222&aaa=1111
(3) applying pattern '^/function/([^:/]+):([^:/]+)$' to uri '/function/ccc:333'
(2) rewrite '/function/ccc:333' -> '/function?ccc=333'
(3) split uri=/function?ccc=333 -> uri=/function, args=ccc=333&bbb=2222&aaa=1111
(2) local path result: /function

あってる?