Some help understanding video ip and dma

in pynq base overlay the video ip documentation its says that bgr is represnted as 24bit and greyscale with 8 bit perpixel when i write single frame to the memory in i want to read it using a32 bit axis bus on the dma how is each pixel is read is the 32 bit will give me 24bit for one pixel and 12 bit for the next pixel meach means one and a half bgr pixel per clock cycle and 4 greyscale pixels per clock cycle and if so how is the the data devided is the whole pixel is lsb and the the other half is msb or otherwise?