Something I put together a while ago, I am fully aware it's not the most realistic skin and/or setup, but it's better than nothing.
Download the Required Model: https://www.gta5-mods.com/vehicles/volvo-alexander-alx400-dublin-bus
Replace the textures within the .ytd with those provided in the download.
TfL Bus Skin/Textures: AOldfield
Original Model: vithepunisher (5Mods)
Any issues drop a comment below, cheers.