I am not sure if my answer arrives at you late. I wish this answer is informative anyway. In fact, the marketing research in general has a very tight association with psychology. If you review some articles from diverse journals in the field of marketing, you will easily find that almost all marketing research is more or less based on psychology. So is the commerical marketing practice.

Therefore, it is very hard, if not possible, to discuess the general topic in a thesis.

What you mentioned, such as the color and scent, is in fact a specitic topic in marketing (i.e. sensory marketing) and the underlying mechinism is identical (i.e. embodiment in psychological term). Therefore, it may be a good idea to depen this view by collecting more empirical studies and finding more mediators and moderators. You may also disscuess the limitations and opportunities about applied embodiment in marketing. For sure, this part can be challenging.

Taking a more macro view, you can find other classic theories, mechanisms and findings standing in the intersectional area. For example, you may heard about elaboration likelihodd model (ELM) and hierarchy of effects/persuasion. These two are very classic marketing theories. ELM elaborates on the information processing and decision-making process in the context of marketing; the hierarchy model is more related to an ideal model of rational decision making. Thus, they are also psychological, even though they are more well-known in marketing.

Contrary to this, you can also find a vast set of classic psychological theories which have been applied in marketing practice. Mere exposure effect is well documented and explained in psychology. It is also widely applied in packging and advertising strategy. Projection theory is also used to predict consumers' mouth-to-mouth product recommendation. Even gender theories were used to establish brand image, shape brand position and interact with targets. What I said is just to name a few...

Thus, again, it is difficult to approach your question without any constrain. Several strategies for you:

1. Focusing on one critical psychological theory and discovering its diverse application in marketing;

2. Focusing on one step of marketing (e.g. persuasion) and summarizing different psychological mechinisms ulitized as much as possible;

3. Using a macro marketing model (like 4P, hierachy model, etc.) as a framework and reviewing related studies for each component under the model.

Tips: as I said at the very beginning marketing and psychology are very tightly related. So a large number of marketing studies were published in psychology journals. Occasionally, marketing studies were published in economic journals. At times, some spelendid marketing related studies are published in neuroscience journals, especially given the neora mania in many fields. You may also read some books on this topic such as Schmitt, Brakus and Zarantonello, (2015).

Schmitt, B., Brakus, J. J., & Zarantonello, L. (2015). From experiential psychology to consumer experience. Journal of Consumer Psychology, 25(1), 166-171.