Standard LEDs can only show one colour. It is determined by the semiconductor material inside the LED, not the colour (if any) of the plastic case.
However, bi- and tri-colour LEDs are also available, these are really two LEDs in one case. For example a tri-colour LED with red and green LEDs can show a third colour, yellow, with both red and green on. Some intermediate colours are possible by varying the currents to the red and green LEDs to change their brightness, for example an orange can be achieved with red bright and green dim.
For more information on standard, bi- and tri-colour LEDs please see:
www.kpsec.freeuk.com/components/led.htm
This page also shows LED displays (at the bottom), the dot matrix type may be of interest to you. For a very large display (you mention 3mx3m) I suggest contacting a supplier direct because there may be specialist units which can be adapted. |
