For the February ATC swap, I made a rainbow ATC for someone. I experimented making several of them before I picked my favourite to send out.
This first one with crayon resist and markers didn’t work too well.
This one is acrylic, collage, and marker
Crayon resist and markers
Acrylic and markers
Acrylic and markers
And the winner was…
Crayon resist and markers
I adore your winner, but…even though some of your attempts didn’t come out as vibrantly, they work all together as a collection, variations on a theme. 
I totally agree with wittychild. Though, shocking exactly no one, my favorites are the grungier ones middle- and bottom-left.
These are all so bright and cheery!
Lovely ATCs!
Congratulations! Your colorful ATCs are a Featured Project!!
Aww thank you so much 
