I'm assuming that is from the Loader tab on the left.
Normally you would click one to select it then use the RGBA sliders below to change the color.
Items get put there automatically with moreclothing's +reghue option. T
To show/use the item it will be found in the Scene tab under their categories.
In this case the clasps are under Collar and Tentacle Monster is found under one of the Body options.
