Ah, the famous "oops" shelf...
It is certainly viable. Forget about the 2 oz bottles of Micromark. Instead, go to Walmart and get the $1 bottles of hobby acrylic. Latex and acrylic are both water-based, so there is no issue mixing them.
You may find this shocking, but I have even occasionally used small amounts of oil paints to get the colors exactly right. The world did not end.