The move took NSW one step closer to becoming clear of equine influenza, said Primary Industries Minister Ian Macdonald.
"This is another step towards having NSW horse flu free by the end of March," he said.
"There are currently infected horses on less than 50 properties in NSW and no new EI infections have been detected since December 21. These are certainly hopeful signs."
Mr Macdonald said the co-operation and support of horse owners has been crucial in getting to this point.
"They must remain vigilant and continue their efforts until we have finally won this battle. Only then can we reap the rewards for all the hardships endured over the last five months.
"It remains vital in the short term to report sick horses, enforce bio-security and abide by movement restrictions."
The areas that have gone to amber are: Dubbo, Wellington, Narrabri, Gunnedah, Parkes, Forbes, Walcha and parts of the Grenfell district.
"These areas are now part of the lower risk amber zone where there is still a risk of infection, but no known infection," the minister said.
"The green zone has also been marginally increased by less than 1% of NSW to free up movement restrictions for some horses previously in the amber zone.
"Extending the green zone has enabled movement restrictions to be eased in some areas near Dubbo, Wellington, Young, Southern Highlands, Illawarra and along the Queensland border.
"A total of 86% of NSW is now protected green zone, 9% is amber, 2% is red and 3% purple."