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Colu
Colored Coins 2.0: a coloured-UTXO protocol over two carriers, OP_RETURN and bare multisig, whose identity is a pure function of chain data.
Colu 0.02 % of the chain's bytes in Book A, as of block 972,299, 2026-10-20 09:30:48 UTC
Colu is the company behind Colored Coins 2.0. In BTI's token table its tokens are Colu assets, each identified by an asset id. BTI is its indexer: it is a native protocol, read by BTI's own colu decoder.
How Colu writes to Bitcoin #
BTI's Colu attribution study (2026-08-05) gives the encoding. Every message is an OP_RETURN whose push begins with the magic 43 43 (ASCII "CC"), a version byte (0x01 in 2015 and 2016, 0x02 from 2016) and an opcode. Over blocks 300,000 to 699,999 the study counted 63,916 issuances, 208,578 transfers and 288 declared burns. The two versions overlapped for 5,767 blocks, so a reader must accept both.
Some issuance and transfer opcodes (0x02, 0x03, 0x11, 0x12) split their metadata: the hash goes into a bare multisig output beside the OP_RETURN. The study proved this by joining carriers: every 0x02 and 0x11 transaction in the sampled range has a 71-byte multisig carrier. A Book B built from the OP_RETURN marker alone would miss those bytes. This is the roster's "two carrier kinds".
An asset's identity does not depend on its metadata. The study overturned the earlier view that it did: a Colored Coins asset id is Base58Check(padding ‖ hash160 ‖ divisibility), computed from the issuance transaction's own first input and on-chain policy bits. The metadata behind the torrent hash is gone (a live probe found zero peers), and a name is only a label.
How BTI attributes its bytes #
The decoder runs in replay mode, a coloured-UTXO walk over both carrier kinds, and the roster notes that every block must be read. Book C is zero for every Colu claim. The hashes are pointers to off-chain bodies, not bodies, so the study classes Colu as a pure-ledger protocol. In its words, Colu spent "331,440 bytes of Bitcoin, permanently, to commit to a name nobody can read".
Colu has two ways for units to leave. Declared burn opcodes were used 288 times, all of them 0x25, between blocks 438,725 and 487,748. Separately, unrouted units default to the last output, the custody drift CoinSpark also shows. The study says supply deltas must keep the two kinds of burn apart.
Findings of the August review #
The BTI protocol review of 2026-08-29 found that Colu and Open Assets answer one question in opposite ways. When a protocol-unaware spend destroys the colour, Open Assets declares the claim None, zero in every book, while Colu declares it riding and keeps its full measured Book B. Those burn claims carried 38,748,707 bytes, 25.16 % of Colu's Book B. Ruling U4 says such a question should be answered once, in the shared layer.
The review also corrected the token table. Its note says five transactions co-carry Colu's marker with another protocol's; the review found four, and they are not Colu: 3-byte payloads with zero claims.
Live figures #
Colu holds 0.15 GB in Book A, 0.02 % of the chain's bytes and 0.12 % of all Book A, with 0 bytes in Book C. The books count 54,888 assets across 412,068 operations, from block 364548 to 972125 (as of block 972,299, 2026-10-20 09:30:48 UTC).
The BTI handoff of 2026-08-16 recorded 138 MB for Colu in the books then covering blocks 0 to 779,999.
Related #
Sources #
Live figures: protocols as of block 972,299, 2026-10-20 09:30:48 UTC. Refreshed hourly.
Updated 2026-10-20 · This page as Markdown