This is a very vague question. If you want specific numbers you will have to read journal articles on experiments that measure conduction band offsets. If you want a qualitative answer, you know AlAs/GaAs is a type I band offset, with AlAs having the larger band gap. And when you have GaAs/GaAs, there is no offset. So as you increase Al concentration, the CBO will increase all the way to the max CBO of AlAs/GaAs. To find the exact form of the increase in the CBO you need to read journals.
I just told you why Al increases the CBO. Since it increases the band gap, and you also know the initial % Al = 0 then CBO = 0 and the final % Al = 1 then CBO > 0. Therefore as you increase Al concentration you must increase the CBO.