Ok i got your point
I don't remember may be it was day before yesterday or the day when nopCommerce team launched 1.5 version, many community members were asking nopCommerce team about this feature, as they were expecting that may be in 1.5 version this feature will be there but sorry to say, currently there is no feature like that in which you select the attribute and color changes etc
BUT you can do one thing, there is 1 alternative i can suggest you
add a product, just like you add a normal product from admin section, You will notice that when you add a product after saving, it becomes a Variant
So you have to make use of variant in order to accomplish what you want
Lets say you want to give 4 color choice to your customers,
when you save a product it become a variant, so we will count it as 1st variant
not create 3 more variants and with each variant add a different color image, name your variants as, Red, Black, Blue, White (any color of your choice)
Remember Red Variant should have red colored image
Black should have Black and so on
If there is no difference in price of any color, then keep price same for each variant
after creating all the variants , it should look like this:
http://img101.imageshack.us/img101/525/colord.jpg Now, add attributes in the first most variant, as Red, Black, Blue, White and make it as dropdown, checkbox or anything
save it and go to the product page and see how it looks:
it will display 4 different images of different colors, so customers will be able to see the product in all the available colors and in the attribute they will select what color they want to when they will place any order you will get the result they chose in attribute
Your product will different colors will look like this on your website:
http://img715.imageshack.us/img715/8437/color23.jpg