How long should I wait before painting a concrete patch?
According to the datasheet (PDF), it reaches foot traffic compressive strength within one day and you can drive vehicles over it within three days, but doens't reach full compressive strength until 28 days. The PROPER answer here is probably 28 days, which is pretty consistent for any concrete products. 

You can probably safely paint it within three days, but I'd be worried that concrete wouldn't reach full compressive strength or that the bond with the underlying concrete would be affected by moisture not having any path out.