The majority of the new-look red paintwork is complete, and English Heritage said ironwork repairs were going to plan.
Tom Jones, of English Heritage, said: "We are pleased with the progress we are making in our vital conservation project on the Iron Bridge.
"We are grateful to our passionate team of staff and volunteers."
The red colour was chosen after forensic analysis revealed it was the original colour of the bridge.
The work is being done as part of a £3.6 million conservation project by English Heritage.
It is the single largest conservation project undertaken by the charity since 2015. The work was started after extensive surveys of the area revealed that the historic structure was under threat from cracking due to stresses in the ironwork dating from the original construction, ground movement over the centuries, and an earthquake in the 19th century.
The project began in autumn 2017, and the charity says that conservation of the different elements of the bridge is well under way. A protective layer of primer has been used across the bridge to prevent corrosion, and replacement iron wedges have been cast and are being fitted.