A white light can be low. A warm light can be bright. Red is a color, not a synonym for dim. Once you separate the color of a light from the amount of it, choosing a setting becomes much simpler: first decide what you want the room to look like, then decide how much light belongs there.
Color changes the appearance.
White light comes in different tones. Some look more yellow; others look more neutral or blue-white. You will often see those differences described as warm and cool. They are descriptions of the light's appearance, not the temperature of the lamp itself.
For white light, the Kelvin number on a specification sheet describes that color appearance: lower numbers generally indicate a warmer-looking white. Red is a different color choice. It is not simply another name for warm white, and it should not be compared as though it were just a lower white-light temperature.
Brightness changes the amount.
A brightness control lets you increase or reduce the light output. When comparing lighting products, lumens describe output; watts describe power use. A color name, on its own, does not tell you how much light a lamp produces.
A numbered brightness setting is useful for returning to a choice you liked. It is not a standardized measurement, however. Level three on one lamp is not necessarily the same output as level three on another. The setting number and the product specification do different jobs.
Make one choice at a time.
Start with the room, not the maximum setting. Keep the lamp in one place and compare the available colors. Look at the nearby wall, your furniture and the objects you normally have around you. Choose the color you prefer before changing brightness.
Then increase or decrease the output while keeping that color. This is especially useful when you like a warm tone but do not want a dim corner, or when you want white light without making the lamp the strongest visual feature in the room.
Choose for the actual room.
Make the comparison where you intend to use the lamp, with the other lights you usually leave on. A bright window, an overhead light and a nearby shade all belong to the setting you are choosing for. There is no need to find a single setting that suits every situation.
Keep the combinations you actually like: perhaps a white setting at one brightness and a red setting at another. You are choosing the appearance of your space, not trying to make every color use the same number. Neither control has to stay at the setting you tried first.
The useful distinction is simple: color answers “which light?” Brightness answers “how much?” Having both choices gives you more ways to get the appearance you want.
Further reading: ENERGY STAR on brightness; ENERGY STAR on white-light color.