An option w/ movable separators:
260:abc:1234:9876:fe::1
Actual IPv6 standard (and also allowed w/ movable separators):
260a:bc12:3498:76fe::1
The problem with movable separators is in handling zeros. If the separators are a known distance apart, zeros can be deduced. The example above has only one zero. Imagine it were a different address: 260a:0:8:65::1 Now with movable separators the the zeros would be explicit because you don't know how far apart the colons are n the address. In your example, it would become: 260:a00:0000:0800:65::1 because there is no way to tell from a movable colon address how many places the colon was moved and how many zeros there are between them. You can move colons as long as zeros are explicit but you must have fixed colons if zeros are implicit. Otherwise there is no way to deduce where the zeros go from simply parsing the address.