Hello! :)

[puggsoy]

@puggsoy Thanks! That's the link I have been searching for but failed to find it anywhere I clicked. This is great!

Question: what is the color code for cyan or magenta? And how do I know if it doesn't conflict with the sheet? Sorry for not being a very artistic person, my fellow designer once called me "a programmer who make ugly graphics", so I don't really good at image editing...

Another dumb question: And since PNG support transparency, why can't the background to be transparent instead? I mean tSR have a very nice site design, with a carefully chosen background color designed to display the sheets for its best viewing experience, why not use transparent background to accumulate that?

Colour code for magenta is #ff00ff and for cyan is #00ffff; these are often recommended since they're unlikely to conflict, but any colour (that isn't too dark or bright) should be fine. To check if the colour conflicts you can use the colour selection tool (this is what it's called in GIMP, not sure about other programs). Just select the background and check if any part of the sprites are selected.

The reason we prefer opaque background is because historically (and still today) not everybody who uses the sheets uses (or is able to use) a program that supports transparency. While this is admittedly a bit rarer today, it's something that's always been done and there's no real reason to change it, since manually removing the background is not terribly hard if that's wanted. Also, carefully chosen background colours can complement the sprites nicely and just make sheets much more pleasant to view.