Yes—brightening an RGB image generally means increasing the pixel values. To preserve color balance, the usual approach is to scale the R, G, and B channels by the same factor rather than adding a fixed offset.

In other words, multiply each channel value by the same amount. That raises brightness while keeping the color ratios the same. Adding a constant to each channel can shift tones and is usually less desirable if your goal is simply to make the image brighter.

One caveat: the “correct” amount of brightening depends on how the image data is encoded. Image data may be linear, logarithmic, or gamma-encoded. Many scientific images are stored linearly, in which case simple scaling is often appropriate. If the data is not linear, brightness adjustments may behave differently.

So, in principle: yes, brighten by increasing RGB values, preferably with a multiplicative factor applied equally to all three channels.