THE latest addition to the successful TravelMate notebook computers, made by Texas Instruments, has just been launched in Hongkong. The TravelMate 4000E WinDX2/50 active matrix colour notebook will sell for HK$39,380. It has a 486 DX2 50 megahertz processor, and comes with four megabytes (MB) of main memory - expandable to 20 MB - and 200 MB of hard disk. The notebook offers 256 colours simultaneously on an Active Matrix Display. Software includes the pre-installed MS-DOS 6.0 and Windows 3.1. Texas said the keyboard had been improved, offering four millimetres of travel for keys, for a natural desktop feel. Battery life of the machine is about three hours. ''The notebook provides the ultimate blend of 486 power, portability and colour in the award-winning TravelMate tradition,'' said Allan Ip, the general manager for Texas' peripheral products division. ''Texas established the performance standard with the 486 WinDX2/50 monochrome notebook as acknowledged by PC Magazine's Editor's Choice Award in May, Portable Computing's Product Excellence Award in April/May, and Windows Sources' Experts' Pick in February. ''Our new WinDX2/50Active matrix colour notebook sets an even higher performance standard for colour notebooks.''