Look at the Layer Values in the Image Object Information window. From here you will be able to determine the pixel value/DN/radiance/reflectance (or whatever your image format is). You will have to add these Layer Values from the Feature View window:
Feature View > Object Features > Layer Values > Mean > [right-click] Layer... > Display in Image Object Information
Simply select a pixel or segment within the viewer and the values for each of the bands will appear for that region of interest. For example, in this screenshot I selected a very "green" object in an ag area. My imagery has 4 bands (R, G, B, nIR). nIR has very high reflectance values off of healthy green vegetation, so you can see that layer 4 is clearly nIR. Conversely, nIR will have very low values when you select an object over water, as water has very low reflectance at nIR. The red band is also very easy to determine strictly from looking at the layer values. Since healthy green vegetation exhibits low reflectance in the visible red, values here will be the lowest among the 4 bands. Blue also has lower reflectance off vegetation, while green has higher reflectance off vegetation.
In sum, you can see that layer 4 = nIR band, layer 1 = red band, layer 2 = blue band and layer 3 = green band.