PCB trace width in LED matrix

So I am trying to design a matrix of LEDs using CCDs with a separate voltage rail for red, blue, and green. I plan on making a PCB to do this but am having trouble coming up with the correct trace width. If my matrix is 8x8, and the LEDs draw 40mA a piece, then I end up with 2.56 amps. This would be for one long trace connected to all of the LEDs. If I make it a grid based lattice structure, can I just split that up evenly with some oversize? The farther away from the power source may have some voltage ripple I guess.

My first thought was to make one long trace down the middle and branch off with smaller ones tying in for rows of LEDs. It seems like if I do a grid based system I could have smaller traces all across the board and save space. I am just now sure how you calculate that though.

Get the PCB toolkit from Saturn PCB (Google it), it will aid you in working out track widths (and lots more).

Its OK to run a pair of tracks for the power and branch off, just ensure they are a pair and your not making big gnd loops etc.