We purchased a Mega Bloks 8120 and on the diagram it showed different colour bloks which included Yellow. when we opened it there was no black or yellow. What should we do?

Often diagrams show combinations of sets that are for purchase in other sets, we had to learn this the hardway too. In small writting there should be an anouncment that states that some blocks are not included that are used in the diagrams. It is the same with Lego blocks, Imagianex, and other sets used to build or creat diagrams or buildings. I have returned to stores and have asked about the diagrams in confussion my self untill I noticed the disclaimer that states other sets were used to creat the diagrams. You might want to find out what the set is that has yellow and Black so that you could purchase the collection. If you lived anywhere nere FortSill I could have helped you out with three large boxes of Mega Blocks left over from my 5 children and a daycar I use to run.