Indigo was originally Rainbow 5, and was the first Rainbow route.
The number five changed the styling and colour.
The logo changed a bit, and the number five was changed slightly with a new colour.
This route got a huge change, the Excels turned into Solars, with new features: bigger buses, more seats, leg room, space age technology, audio announcements, real time tracking, and a new timetable. This was the first bus to have the 2002 Trent Barton livery.
Rainbow 5 got a stylish makeover, with new Eclipses, and more new features: air-con, a new name, leather seats, and an updated timetable.
Starting in late-July 2011, Indigo runs all day, every day and is the first bus to run 24/7.
All the Indigo buses got a major makeover and the frequency went from every 6-7 minutes - to every 5 minutes, and now, every 10 minutes to improve reliability. There was a slow transformation, causing the old Indigo buses to all be refurbished by 2017.
In 2018, the colour looked a bit darker, and the 24/7 was dropped from the logo, but is seen 24/7 from Long Eaton to Nottingham.