0x00 - No brick... just empty space.

The "original" bricks:

0x01 - Normal blue brick
0x02 - Normal yellowish-green brick
0x03 - Normal pink brick
0x04 - Normal purple brick
0x05 - gold, indestructable (mostly) brick
0x06 - 4-hit gray brick
0x07 - invisible, becomes 0x03 when hit.
0x08 - 3-hit gray brick
0x09 - 2-hit gray brick
0x0a - 1-hit gray brick
0x0b - gold, 1-hit-required indestructable.

New bricks for v3.0:

0x0d, 0x0e, 0x0f, 0x10 - Blue, light to dark
0x12, 0x14, 0x15, 0x16 - Red, light to dark
0x11, 0x17, 0x13, 0x0c - White to dark gray

0x19, 0x1a, 0x1b, 0x1c - Cyan to dark green
0x1e, 0x20, 0x21, 0x22 - Pink to dark purple
0x1d, 0x23, 0x1f, 0x18 - Orange, yellow, blueish-green, EXPLODING BRICK

New bricks for v4.0:

0x25, 0x26, 0x27, 0x28 - Green slime (four variations)
0x2a, 0x2c, 0x2d       - Red, Green, Blue "unlocker" bricks
                  0x2e - Gold-exploder brick
0x29, 0x2f, 0x2b       - Red, Green, Blue "locked" bricks
                  0x24 - Blue-expander brick

0x31, 0x32, 0x33, 0x34 - All these last bricks are the
0x36, 0x38, 0x39, 0x3a - "color wheel" bricks, whose
0x35, 0x3b, 0x37, 0x30 - colors basically go around the
0x3d, 0x3e, 0x3f, 0x40 - outside of a color wheel,
0x42, 0x44, 0x45, 0x46 - changing hue as they go.
0x41, 0x47, 0x43, 0x3c - Not exciting, but useful to
board designers who complain that they never have the
colors they want in the boards they design.  Most of
these bricks look pretty bad if you don't have AGA.
