ColorMixer | ColorMixer is a widget for choosing a color in HSV | Widget library

All of the components must be specified separately, and the range of values is [0, 1], not 0x00-0xFF.

This works:

This is not ASP.Net but I am pretty sure the same would apply. I do not think you are using the right event for what you are trying to do. The event CheckBoxList1_SelectedIndexChanged fires, every time the user clicks into the CheckBoxList and changes which item is selected. The event fires even if a check box was not changed. Granted, you could do what needs to be done here, like check which check boxes are checked and pass some variables to a method, however You will do this EVERY time the user changes the selection.

I am guessing a button would be a better control to fire your color method. This way you are not looping thru the items until this button is pressed. Then, you can loop through the list and grab the checked colors. It is not clear what you want to do if there is only one (1) color checked or three or more, since the post indicates you wanted to pass only two colors.

Below (c# code) is the code I used with a CheckedListBox where items are named Red, Blue, Green and Yellow. I used a Button_Click event instead of the CheckBoxList1_SelectedIndexChanged event. When the button is pressed it simply loops through the list and displays the item index, name and its checked state.