A GENERATION ago a young man with a rucksack crammed with spray paint cans would have been questioned closely by police.

It wasn't so much the depressing information that he was probably going to deface a wall somewhere, it was the fact that graffiti then rarely consisted of much more than an uninspiring slogan such as "Tongs Ya Bass". Thought-provoking haikus they were not.

Now though in Glasgow's city centre, you might have noticed a fresh era of spray painting which is large, bold, and frequently funny. Well, have you ever considered that Daleks might be freely floating below the water in the River Clyde? Or why is that giant cat licking its lips while looking at a bird-cage which is empty other than for a few colourful feathers?

Glasgow's council leaders, not often in the front line of innovative ideas, have embraced colourful murals to freshen some drab city walls, and are even putting money aside to pay for it. The old Glasgow gang slogan writers will now be kicking themselves.

Not everyone is convinced. When other cities such as Detroit used murals to conceal some of the worst aspects of urban decline, critics rather sniffily described it as akin to putting bright red lipstick on a corpse. Even Glasgow comedian Frankie Boyle once observed: "Seeing a beautiful mural on the side of a building just means that you're in a really crummy neighbourhood."

But let's not be too cynical. There is a quality here in Glasgow's murals which are arguably of a better technical finish than some of the daubings inside the city's art galleries. It's curious that if you paint a picture on the inside wall of a church, for hundreds of years people will reverently travel miles to gawp at it. Paint on the outside church wall and someone will want to report you to the authorities.

However Glasgow City Council is so delighted with the quality of murals that it has published its own City Centre Mural Trail which takes you from underpass to disused factory, to bridge arches in order to see the best that spray paint can offer. And they are spectacular.

That's if you ever stop to look at them of course. Familiarity does indeed breed indifference if not contempt. My favourite is on the side wall of the Old Fruitmarket at the back of a street car park on Ingram Street in the Merchant City. Most Glaswegians are simply scurrying past, lost in their own thoughts rather than drinking in the scenery around them. But stop to have a look. A real look. Imagine you are indeed inside an art gallery. The mural is a trompe l'oeil with the wall seemingly breaking open to reveal wildlife scenes of Scotland with squirrels, foxes, badgers, Highland cattle and hedgehogs in lush vegetation. Ignore the folk leaning against the wall having a fag, and go up close. There are individual hairs on the badger that you can pick out. Part of the wall is corrugated iron yet the painting carries over the ridges as if they were not there. And all done with a spray can. Next time someone claims how difficult it is to spray a garden fence with creosote, tell them to look at this wall, to see what real hard work is.

This is painting on a grand scale. But there are smaller works. An underpass beside Cowcaddens Subway station - now underpasses really are places that people scurry through with little eye contact - is worth a minute or two of your time. The artist has cleverly painted hands making shadow pictures, something we all did as youngsters. That in itself is clever as the hands and fingers are arranged to make shapes further up the walls. But look at the hairs on the back of the wrists, painstakingly painted in. Or the loops and whorls on some of the older hands. It's genius.

Then for sheer amusement there is the River Clyde painted on a block of flats on Clyde Street near St Andrew's Cathedral. While the actual Clyde opposite is a lot more sedate, this Clyde has a view under the water where Daleks may be hiding, or swimming elephants, or shoals of colourful fish. Secretly you really do wish that the Clyde was like that.

It is the work of Bobby McNamara, who calls himself Rogue-One. He did indeed start years ago, simply tagging walls, putting his initials on empty concrete before moving on to larger paintings. Now his hobby, which must have been slightly frowned upon at times, can now earn him money. Looking at the River Clyde he created, Bobby remarks: "The scary part was climbing the ladder. Once the background colours and outlines are ready the fun part of painting begins. Almost a month of work was spent on painting, moving from panel to panel, top half and bottom half and finally finishing details. Hard work but fun."

As to the reason for doing it, says Bobby: "Glasgow like any city needs colour, and people are enjoying seeing these large murals starting to pop up around the city. Well I would like to think they are. As one person said to me, it brightens the place up and gives you something to smile about on the way to work." The city's population it seems has moved on since the days of his first mural for the city when an elderly woman did come up to him and angrily say: "I'll get the police to you."

Hopefully the best of the murals will remain and will be appreciated for years to come. Others though are on temporary walls surrounding vacant land. Lets hope for the sake of the city we don't need too many of them in future years.