I have a few categories in my application regarding the various needs/dimensions of human lives such as health, social services etc. I am not sure which color would best represent each category. Could you please introduce a reliable source on the psychology of colors (from a UX perspective) to me?
It's necessary to have go with a ux project, having some color (should be match to the psychology), but before that you should know who are your USERS. I am saying this because color has different meanings in different countries. The world's maximum country thinks of red as the symbol of blood, danger, or war; but China and Japan take it as peace. Some think red is the color of love too... so it's a bit confusing.
Here are some color suggestion guides that are widely used by designers. Their psychological meanings are accepted world-wide. You can pick yours from below.
Blue : Blue is one of the most commonly used colors in product design. The blue color is considered to give emotions such as trust, safety and relaxation. Blue's various color shades can create a different set of emotions. Light blue, for example, creates emotions like calmness and makes the user feels refreshed. The color blue is also associated with happiness.
Pink : The pink color is a color which is related to candy and sugary items. Most of the time it is called a “Girl’s color” by many people; however, the color pink is not as feminine as you think. It is a color of playfulness and joy.
Black : The black color represents power and formality. The black color is considered to be the strongest color of the spectrum. Black fonts have been there from the black and white age until the electronic age due to its ability to create a proper emotion of power over other colors.
Green: For obvious reasons, humans find green to be a color that is connected to the environment, trees and plants. Most of the time, organizations that sell organic food and beverages use the green color for their application.
Red Red is a color that gives us the sense of importance and notifies us about danger as well. Red often denotes places where the user should pay special attention. For example, in traffic lights, we show the color red as an indication to stop crossing or to stop the vehicle. At the same time, the color red can be taken as a symbol of love and passion. But most of the time, red is used in places where the user needs immediate attention.
NOTE: The color palettes common in, and presumably preferred in, Asia are very different from those in the West. For example, white is associated with death in most of Asia in the same way that black is in the West. This is an indication of how the differences can be “black and white”. So pick your user base first, then it will be easier to choose your colors.
This seems like a difficult question to answer without knowing more. If it were me, I'd ask the following questions:
1) What is the app? What are the primary use cases?
2) How are users feeling when they use the app?
3) What are the brand guidelines for color?
4) What do you want to convey with the categories?
5) Are you using any icons or illustrations, or are you only using title and color?