The other one is well is the Cobalt service?, the 309-310 (new service is 311)? , weren't the buses just branded Cobalt?, but since revamp it now includes the coast to Blyth? (advertising the service to Blyth where before it wasn't much highlighted?)
The Coast Road corridor has been through various incarnations over the years. I should know, I live on it!
The Cobalt Clipper, as was, introduced in 2008 as just the 309. It was half hourly, running from Newcastle to Blyth broadly following the Arriva 308 route. It had Scania Omnicities at the time.
The Citylink 58 was introduced at the same time with much fanfare from Heworth to Hadrian Park, via Newcastle. It ran every 10 minutes with then brand-new Citaros.
The "Centurion" 75/76 then handled the bulk of the Haymarket-Coast Road-Coast services, running in two different directions around a large loop of North Shields/Tynemouth/Whitley Bay.
The 309 ended up doing quite well and was increased to every 15 minutes. The 75/76 were also binned off and the Newcastle-North Shields segment replaced by a new 310, joining the Cobalt brand. This somewhat simplified the Newcastle-Coast routes into two, running at a combined 7.5min frequency up the Coast Road. The route ended up getting extra Citaros in 2010 to go with the Omnicities, and subsequently a batch of B9s in 2013/4.
The 311 was only introduced last year (perhaps late 2019 actually). It replaced what was the 58 then the 57, with GNE clearly wanting shot of a route that ran from Heworth (later Wardley and Heworth) all the way to Hadrian Park and had been allocated a weird mix of Citaros, Artic Citaros, Versas then somehow ended going full circle and getting the original Citaros back! That route, having started as every 10 minutes in 2008 was gradually reduced to every 20, then it lost its evening service entirely, then at one point you'd have random gaps in service in the peak so that they could run a '58X' from nearby Cobalt Business Park straight to Newcastle. The only bit of route that it exclusively served from Newcastle was Hadrian Park itself and it became increasingly clear over time that GNE didn't want to run it past Newcastle anymore.
The introduction of the 311 kept all of the routes going down the Coast Road in one place (terminating at Haymarket Bus Station) whereas the 57/58 meant that you'd be picking and choosing between there or various random stops in the City Centre. They were also pretty bad for getting snarled up in peak time traffic on the Tyne Bridge.
And so, we're at the present day. What started off as a 58, 75, 76 and 309 across three different brands eventually boiled down into the "Cobalt & Coast" brand.
The 309, every 20 minutes, Newcastle to Blyth.
The 310, every 20 minutes, Newcastle to N Shields
The 311, every 20 minutes, Newcastle to Hadrian Park.
The B9s were also tarted up and had tables fitted. Combined, that's resulted in 9bph between Newcastle and Battlehill (and still a rather cool 17bph down the Coast Road corridor when you add in Arriva's 306/308)
Due to covid the 311 has disappeared from time to time with the 310 picking up the stops around Hadrian Park (which just involves diverging off the usual route, looping the estate and rejoining where you leave off).