Your question is too vague... If you want to ask a question in this fashion then people cannot be bothered to do the background check up's.... If I had to ask this question, I would have posted the make / type / datasheet.. If the matrix has been built from a kit then specify the LED's used..
Normally an LED will be at it's brightest above 20mA... Any more than 30mA and she blows....
You need to supply 20+mA to each one.. Either deduce power used (if they are multiplexed) and design around it.
When using multiplexing, it is similar to PWM ie.. On time vs Off time... Apparent brightness can be altered by manipulating the current so the average current through each LED is above 20mA..