Without his own clubs -- which were lost -- Barham collected six birdies and would have held the lead alone if he hadn't made a finishing bogey from a bunker at the par-4 18th.
Still, the Englishman holds just his second first-round lead on the European Tour despite missing not only his clubs, but also his shoes.
'I was only able to walk the course on Tuesday,' said Barham, referring to playing without a practice round. 'There was still no sign of the clubs on Wednesday and it took me a couple of hours to get some new [ones]. I tried to get everything to match what I had, but the irons are completely different.
'I have never hit driver so much just because I didn't want to hit the 3 wood.'
Using his own clubs, Colsaerts also carded six birdies and one bogey -- with the bogey coming at the par-4 17th. Playing for his tour card this year, the Belgian has held at least a share of the first-round lead twice on the European Tour, but not since 2004.
'I just keep knocking on the door,' he said. 'People know I can do better than I have showed so far.'
Of the leaders, only Warren had a spotless scorecard. Playing in one of the earliest groups, the Scotsman carded just one bogey on the front nine, but back-to-back birdies from the 12th and 15th put him in the clubhouse with the early lead.
The European Challenge Tour's top player for the 2005 season, Warren is encouraged by another former Challenge Tour player's success this year.
'Johan Edfors has had a dream season,' he said of this season's only three-time winner, 'and the guys who have won on the Challenge Tour are getting results on the main tour. If I can be one of those guys and kick on, I'll be delighted.'
Fredrik Andersson is the top Swede after one round, leading a group of five players who are tied for fourth place at 4-under-par 68.
Andersson was joined by 2005 U.S. Open champion Michael Campbell of New Zealand, Scotland's Alastair Forsyth, Frenchman Raphael Jacquelin and Tom Whitehouse of England.
Swedes Peter Hanson, Fredrik Jacobson, Jarmo Sandelin and Henrik Stenson lead a group of eight players who share ninth place at minus-3.