Version 4 ICC Specification
Version 4 of the ICC profile specification was published in 2001. The v4 profile format has introduced a number of changes when compared to the previous v2 specification. These changes provide a number of advantages, the most significant of which follow from the removal of ambiguities from the specification and a more precise definition of the PCS. More information about the advantages of the V4 specification can be found here.
These lead to an improved predictability of performance of a profile in use which will lead to a reduction of major differences of interpretation. Therefore, when pairs of profiles are used they should always produce the same result - regardless of which CMM is used. A summary of reasons to use the v4 specification is available.
As color management requirements evolve, the profile specification undergoes a process of continuous review by members of the ICC. The current version is ICC.1:2004-10 (Version 220.127.116.11) and is available on the ICC Specification page, together with Amendments approved by ICC members.
The specification has been approved as an ISO standard (ISO 15076) and the version on the ICC Specification page is compatible with the ISO publication.
Most platforms and color management applications have now migrated to ICC V4, or are in the process of doing so. You can test whether your system is V4-compatible here.