( Nichrysalis does a better job explaining it in Spirit Day is Coming.)
What YOU can do!
The color of Spirit Day is purple, so show your support by...
Turn your avatar purple, which can be done with a photo editing program
Feature a purple deviation on your page
Turn your devID purple (again, simple photo editing program)
Use purple emoticons!
Turn your journal skin purple
Make a purple themed deviation, which can be submitted to the new subcategory, Community Projects > Awareness > 2012 > Spirit Day.
These are just suggestions, of course. If you think of anything else you can do to show your support, go for it!
What the emote community can do!
If you know of any purple emoticons, I'd like to feature them on October 19th! Better yet, if you know of emotes that somehow relate to Spirit Day, suggest those, too! Or, make one. Any way you want to do it, I'd really like to get a stellar emoticon feature going for Spirit Day! So note me your suggestions, or comment here.
Actually, if you know of any purple deviations that are related to this event, suggest them to the respective CV! FAQ #18: Who selects Daily Deviations and how are they chosen?
So get to suggesting and go turn your dA pages purple!