The cells shape of foam seed tray can be made into round or square shape. The loading capactiy of square shape seed tray is around 30% more than round shape, and the water is more equally distributed in square shape, which make the plants root grow better.
The foam seed tray color will effect the plant seed root temperature. We always use the white color seed tray in Summer and autumn, because the white color will reflect the sunlight to reduce the heat accumulation in seed root. And in Winter and Spring, we always choose the black color seed tray, because the black color will absorb the sunlight, which will be good for seed root growing. After the seed grows up, we need to transplant them into root control pot to keep its growth.