Since you have not provided the full code, you will have to debug and step through your code to figure out the issue.
Type mismatch occurs when you assign a value to a variable that is not of its data type e.g. storing a number into a string variable.
I would think maybe your RGB value may be looked as an array given it is 3 values separated by commas. Just a hunch, but if you are assigning that to a string then it would mismatch. Try to do an explicit conversion to a string..
https://support.smartbear.com/testcomplete/docs/reference/program-objects/aqconvert/vartostr.html
