Blizzard Colorstorm 252 (B)

with the current fixture profile you cannot. and there is a reason for this. at the moment, Eos can only handle one color picker per channel. this happens (regarding LED) with parameters called Red Green Blue and the universal Hue and Saturation. for your multicell fixture you would need more than one color picker to comfortably control it. so there is a compromise: the current profile lets you control the whole fixture comfortably with a color picker but to do so, you loose the ability to control the cells individually.

there are two ways to remedy that:
-you edit the current profile (Patch > Fixtures > Colorstorm 252 13ch > Copy > Edit) and while you leave the first instances of Red Green Blue, you change the rest to Red2, Blue2, Green2 and Red3, Green3 and Blue3 respectively. you can control now individually but only cell one gets the colorpicker (because it has the parameters Red, Green Blue and not the numbered ones)
-you go and do some editing: you create a "mother fixture" that holds all the general parameters and then you create a "child fixture" holding parameters Red Green Blue (Hue and Saturation will be added automatically). then you could patch the mothe fixture to say channel 110 and the children to 111 thru 113.

i know everything has pros and cons, i guess it's up to you to decide...