We study the statistical properties of melanoma cell colonies grown in vitro by analyzing the results of crystal violet assays at different concentrations of initial plated cells and for different growth times. The distribution of colony sizes is described well by a continuous time branching process. To characterize the shape fluctuations of the colonies, we compute the distribution of eccentricities. The experimental results are compared with numerical results for models of random division of elastic cells, showing that experimental results are best reproduced by restricting cell division to the outer rim of the colony. Our results serve to illustrate the wealth of information that can be extracted by a standard experimental method such as the crystal violet assay. © 2013 IOP Publishing Ltd and SISSA Medialab srl.