are you using the 'Image Reader' from the KNIME Image Processing Extension or the 'Read Images' from the native KNIME nodes? If the first is the case, there is a special 'Image Viewer' view with some advanced configuration options on the right of the view panel. There you can choose the image renderer which should be used. Here, you can select the color base image renderer and check if the color will be displayed. However, in the 'Image Viewer' node view you can always cycle through the color channels (also on the controls on the right) and manually check that there is indeed more than one color channel and that the individual channels contain numbers different from zero.
If that is not the case but your images should contain color then there may be a bug. Then it would be nice if you could upload a workflow reproducing the behavior.
sorry for the long wait. There is a node called ‘Image Viewer’ which has this node view I was talking about. This one should display the colors correctly.