The yellow top tube is mainly used for biochemistry tests, such as kidney function, liver function and thyroid function. The purple topped tube is used for blood counts and blood sugar tests.
When completing my sample, I noticed the yellow top tube had some sort of waxy like substance in it but the purple one did not, is this correct?
Yes, this is correct. The tubes have different additives in them according to the tests which will be run on those samples in the laboratory. It is completely normal that they are different in appearance and it is important that you put the correct lid onto the correct bottle.