AS IS often the case with Wimbledon, what is happening off court can be more interesting than what is happening on it. At this year's championships the British sense of propriety was again in evidence. Spaniard Conchita Martinez became a victim of stuffy dress rules and was ordered to change her outfit, which was deemed to be too colourful. According to the rules, costumes must be predominantly white and carry a minimum of sponsorship labels. The Martinez incident is certainly not an isolated one as more players risk censure with myriad colours and the odd stretch of lycra. Martinez is not the only fashion victim - much of Andre Agassi's appeal lies in his outward presentation. If it isn't his flowing hair or designer stubble, it's his chest hair (or lack of it) that makes headlines. Tennis has always been synonymous with fashion's changing shapes, but until fairly recently did not welcome an invasion of colour to its uniform. The Sunday Morning Post borrowed two of Hongkong's young tennis hopefuls to model the latest in tennis gear. Both teenagers are sponsored by major sportswear companies which are veering away from the traditional whites. Jacklyn Fu, 16, is Hongkong's number two under-18 player. She will be going to England this summer on an official tour and is sponsored by Fila. Rudy Chung, 17, is in the top five for under-18s in Hongkong, and has been an Adidas contract player since 1991. Adidas has been working with Stefan Edberg for almost 10 years, and has recently launched a Stefan Edberg line in exotic colour combinations. ''Our Equipment Line provides simplicity and functionality,'' said Adidas spokeswoman Diedre Chan. ''We not only dress Stefan Edberg and Steffi Graf, but also the weekend player who competes for the club championship.'' Fila sportswear for 1993 focuses on three distinct lines, each containing a wide range of co-ordinated separates to dress the wearer from head to toe: caps, shirts, vests, jumpers, shorts, miniskirts, and many more. Fila is also keen on sponsorship. Eighteen-year-old Andrei Medvedev, winner of the recent Stuttgart tournament, and top-ranking Monica Seles, are both sponsored by the company. There is also a Seles line with mosaic motifs, printed or embroidered in shades of blue, green or warmer orange, combined with stronger touches of violet, light blue, pistachio salmon and red. The line includes pleated miniskirts, warm-ups, baggy jackets and straight-leg trousers. So what do the rising stars think of their sponsors' clothes? ''I love Fila clothes, I think they are great,'' said Fu. ''They are really good quality and their designs are not old fashioned; they cater for the younger tennis player like myself.'' And Chung's verdict? ''Adidas offers good-quality attire with very nice designs, but more importantly they are extremely durable. The shoes are particularly comfortable.'' Clothes by Fila available at the Fila shop in Swire House, Central. Clothes by Adidas available at Ocean Galleries, shop number 232.