Averaging many frames should reduce random noise, but it should not create a strong color cast if the source frames and processing are correct. The most likely explanation is a channel-order bug in your code: red and blue are probably being swapped somewhere during summing or reconstruction.

That fits the result you describe—noise is reduced, but the color balance shifts toward blue. In image/video data, this often happens when RGB is confused with BGR, or when channels are written back in a different order than they were read.

So the stacking itself is not the cause; the averaging math is fine in principle. Check:

• the pixel format coming from the webcam
• the order you read channels
• the order you store/write channels in the output image
• any library assumptions about RGB vs BGR

If those match correctly, the averaged image should keep essentially the same colors as the individual frames, just with much lower noise.