You can't do that using different measures. Instead of that, yo can split between measures using a calculated Dimension with Valuelist (in example, there are other ways, as logic island in script). Doing so, yo just use a single measure expression , and much more important, you can differenciate between one column and other in colour expression. It will looks something like that
Also notice a secons change. If you want to refer to general average for sales, you need to use TOTAL por your average expression ( avg(TOTAL Sales) ). Doing so, you obtein same value (and correct) for all dimensions values.