Convert Gray channels to RGB channels in PNG

[t11s]

I need to create PNGs with 8-bit RGB and Alpha.

Here is what I have:

Format: PNG (Portable Network Graphics)
Type: GrayscaleMatte
Endianess: Undefined
Colorspace: Gray
Channel depth:
Gray: 8-bits
Alpha: 8-bits

But i need it to end up in this format:

Format: PNG (Portable Network Graphics)
Type: TrueColorMatte
Endianess: Undefined
Colorspace: RGB
Channel depth:
Red: 8-bits
Green: 8-bits
Blue: 8-bits
Alpha: 8-bits

I've tried all kinds of things (-type, -colors, -depth) and nothing seems to be able to convert the image from one channel of Gray to channels of Red, Green, Blue.

Thanks!

[snibgo]

-type TruecolorMatte

Edit: I should say: "-type TruecolorMatte" is good if your convert has created the grayscale image, and you want to ensure it is stored as that type.