*Problems with downloaded chipsets*

I've downlaoded many chipsets from the web.
I want to use them i my games but, when I've ass them into RPG Maker the lower layer get a color who not look like the normal layer color.
If I put some green gras on a map it just looks red toned.
When placed another thing like water on the grass, the grass is transpared in the water.
The upper layer looks normal but I can see the normal base/ lower layer.

What's the problem?