I really love street art for a simple reason: it's one of the most democratic forms of art we have in this world, from both the artists and the public point of view.
As for the artists, they don't have to pay a rent for a studio where to work, nor for a gallery where to exhibit their works. This means that street art is accessible to all artists, regardless of their social and economic status.
As for the public, they don't have to pay a ticket and make long queues to see the works. Above all, everybody can usually understand the works, not just those with certain types of educational backgrounds.
In Dublin there are a lot of murals here and there, mostly in the Liberties and in Temple Bar. As for the last one, I would like to suggest that you take a look at the Icon Walk, a multi-street public art installation, which was created in 2010 by the Icon Factory, an artists co-operative that works to produce original images of a wide range of irish cultural figures or icons. Most of artists' works can be found at the Icon Factory Gallery, 3 Aston Place (Temple Bar).
All the murals I've seen in Dublin are in color. I converted to black and white the pics taken at the Icon Walk in order to express my feelings about the great work the artists and the volunteers are doing. This is my way to say "thank you and good luck to all of you".