HEWLETT-Packard, the world's leading maker of colour printers, more than doubled the sale of its colour printers last year. HP sold about two million colour DeskJet printers worldwide, which represents a 122 per cent increase over 1992, when it sold almost 900,000. It sold 120,000 in 1991. By selling two million colour DeskJet printers, HP sold more than all other makes of colour printers combined, according to BIS Strategic Decisions, a market-research firm based in Norwell, Massachusetts. ''Colour printer sales are growing faster than sales for all other types of printers and HP is responsible for most of these sales,'' Richard Snyder, general manager of HP's DeskJet Printer Group, said. HP's black-and-white DeskJet 500 printer was the best-selling printer in the world in 1992 and repeated the feat in 1993. However, the ratio of colour DeskJet printers sold by HP to black-and-white DeskJet printers shifted significantly by the end of the year. HP now sold more colour DeskJet printers than black-and-white DeskJet printers, the company said. ''Colour DeskJet printer sales from HP have exploded because we offer what customers are looking for - high-quality black and colour printing at a low price,'' Mr Snyder said. According to HP and industry research, about 80 per cent of all colour inkjet printers sold last year were HP DeskJet printers. ''Mainstream colour users insist on excellent black print quality and performance before they will seriously consider buying a colour printer,'' Mr Snyder said. ''For those considering colour printers - after their basic requirements have been satisfied - they are telling us they are concerned about colour ease of use and colour print quality. ''Ease of use and print quality are major focuses for our development activity. HP soon will be bringing to the market some real breakthroughs in this area. ''Basically, we plan to do for colour printer users what 35 mm autofocus cameras did for the average, non-technical camera user. We believe these breakthroughs will further accelerate the mainstream's shift from black-only printing to black and colour printing.'' HP has sold more than 10 million inkjet printers since the first one was introduced in 1984. HP sells its inkjet products around the world through a network of computer dealers and value-added resellers. HP has inkjet product divisions in Barcelona, Spain; Corvallis, Oregon; San Diego; Singapore; Vancouver; and Washington.