If we correctly understand, you have different types of images (e.g. RGB, NIR and other multispectral images) that were taken with slantrange. If you use all of them at the same time in Pix4D Software it will create grayscale images.
The first step to see the RGB images, would be to synchronize the camera/drone with a computer. Then, it should be possible to identify which images are RGB and which are multispectral. Then, the RGB images can be used separately from the other images to create a project with Pix4D software, the outputs should not be in grayscale if they are used separately. For multispectral images, the outputs would be in grayscale, but these can be colorized, e.g. if you want to create an Index Map.
For example, in the following article are detailed the instructions for processing RGB and multispectral images with Sequoia camera: https://support.pix4d.com/hc/en-us/articles/209362146-How-to-process-Sequoia-imagery