Decoding errors in the colour code, a promising quantum error correction method, has been proven to be NP-hard, indicating that the computational resources required to solve this problem increase exponentially with the size of the input. This finding has significant implications for the development of large-scale quantum computers, which rely on quantum error correction to maintain the integrity of quantum information. The colour code, in particular, is attractive due to its broad applicability and potential to reduce overhead in logical operations compared to other topological codes. However, the NP-hardness of minimum weight decoding in the colour code poses a challenge for its implementation in practice1. As quantum computing continues to advance, this result highlights the need for innovative solutions to overcome the limitations of current quantum error correction methods. This matters to practitioners because it underscores the complexity of scaling up quantum computers while maintaining error correction, which is crucial for securing sensitive information in a post-quantum world.