The crustacean, normally blue-black in colour, was discovered in the catch of Innes Henderson on the Isle of Coll, to the west of Mull.
Mr Henderson donated the unusual specimen to Deep Sea World in North Queensferry, which said the odds of finding an orange lobster are around one in 10 million.
The bright colour could be down to a genetic mutation, according to experts.
Lobsters are usually only red or orange in colour when cooked. Their shells include a pigment called astaxanthin which remains stable in heat as other colours break down.
Deep Sea World's Tina Coventry said: "We often get calls from people claiming they have found something unusual. However, in this case, Innes really has discovered a true rarity.
"According to the University of Maine's Lobster Institute, this type of colour mutation is extremely rare. In fact they estimate the odds of finding an orange-coloured lobster is around one in 10 million.
"No one is entirely sure why these sort of colour changes happen in individual crustaceans. It may be some kind of genetic mutation or a reaction to some kind of outside stimulus.
"We're not even entirely sure if the colouration will stay the same when the lobster eventually moults. One thing for certain, however, is that no one here has seen anything quite like this before."
The healthy lobster will remain in the aquarium's quarantine area for the next few days and will then be released into one of the marine displays.