I bought some plain white canvas shoes at Target (I went cheap because this was my first attempt at this kind of project and didn't know how it would go) to use and did some sketching on a sheet of paper to get a feel for the size of my Tardis. I used a pencil to sketch the Tardis on the shoe and then used my yellow pen to start adding the base of the explosion. I knew I had to use the yellow first (else it would bleed with other colors and ruin my pen) and add layers of color as I went. It was weird because I'd never really colored like that before. Definitely a learning curve involved in this process for me.
Once I had the toes colored with yellow explosion, I outlined the Tardis.
The outline was probably optional, but I was having a hard time imagining the end result and I really wanted to see it in there, so I decided to just go ahead and do it. From there, I freehanded the swirls and just had fun with making loopy designs all around the shoes.
I had originally made the trim on the shoes yellow in hopes of it breaking up the darkness (and adding to the BLAM EXPLOSION effect) using the natural design effect in the style of the shoe. You'll notice in the final image up top that the trim is black. My coloring hand got a bit unstable a few times and I hit the trim with my blue pen in a terribly obvious place. =( Thus, black trim in the final result.
After I had my swirl base, I used another shade of yellow to outline and then add depth.
Then, because I got a little anticipatory for results (as with the Tardis outline), I colored in the toe of the shoe to get a feel for the way the explosion colors would stand out against the background.
You can see the layers being added in at this point. Oranges, yellows, all the various bright colors I had. It was all random and freehand from this point on. I tried to keep the design sporadic and unpredictable. Once I had all the explosion layers added in, I filled in the blue of the background and the designs on the heel and tongues (which I forgot to photograph in-progress). Once the blue was all in, I used dark purple, a little black, and some neon blue highlight over thinly colored patches to add depth to the backdrop. Overall, I had fun and I'm pretty proud of them. I don't care if they're not the best rendition of the Exploding Tardis, they're mine and I love them.