There is no trick here, just repositioning of the colored blocks. A block seems to be missing because the upper and lower figures look like a triangle but in fact they are not. If the upper figure was a right-angeld triangle, the ratio of the two vertical sides of the red triangle and that of the green triangle within it must be equal. Careful examination of the red and the green trianlges will tell you that the ratios are different.

Since the whole upper figure is not a triangle, there is no missing block after repositioning of the partitions that make it up.