It was listed on the London Stock Exchange and was a constituent of the FTSE 250 Index until it was acquired by Fidelity Investments in August 2015.

Colt was founded in 1992 by Jim Hynes with funds provided by Fidelity Investments as City Of London Telecommunications.

In April 2009 Colt completed an Open Offer raising €199.1m (including a €9.7m foreign exchange gain) before expenses with the issue of 211.0 million shares.

In May 2011 Colt acquired a majority shareholding in MarketPrizm, a provider of low latency market data and trading infrastructure services.

[9] On 2 November 2022, Colt entered into agreement to acquire Lumen Technologies' Europe, Middle East and Africa (EMEA) business for $1.8 billion.