I didn't notice a delay in the color showing up, but it's been almost 5 years since I last bought Color Wonder stuff. (It was kind of a one-time deal with kids I wasn't allowed to set limits for but wanted to entertain in a fun way. ColorWonder saved me cleaning & re-painting my living room walls.)
However, I wouldn't buy it again because it's expensive for what you get! I bought a package of markers & a pad of blank paper at Target. If you REALLY want it, wait for it to go on sale and buy the blank paper.
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Liz
DD (3/2010)
"Make mistakes! Get messy!" - Miss Frizzle