There's another roundabout way to achieve the translucent effect.
It involves using an image processing software such as GIMP, Graphics Gale, etc. I'll use GIMP hereafter for reference's sake.
1) Edit your sprite.
- Load your sprite in GIMP.
- Load the grass tile in GIMP.
- Manually map the grass tile so that you can get the grass portion needed (corner, side, middle, or etc.).
- Make sure your sprite is in on a separate layer from the grass.
- Select the grass layer (eg layer 2), place the desired portion over the sprite, change the grass translucency until it looks just right for you.
- Crop the grass image to the individual sprite in your sprite sheet. (Eg, if your sprite is 32 x 48, the make sure the grass fits 32 x 48 too).
- Merge the layers and save them as a different spritesheet from the original.
- When you create your cutscene/event, simply change your character's graphics to the one you made.
2) Create a picture.
- Again, you'll be using GIMP.
- Map out the entire portion of your grass are or just the relevant ones.
- You may need to manually map the grass tile so that you can get the grass portion needed (corner, side, middle, or etc.).
- Once completed, change the opacity until you are satisfied then save the file. (Opacity can also be changed during event creation).
- When creating your cutscene/event, you can use "Show Picture" to bring up the image, and "Erase Picture" when you're done.
Hime has a Map Screenshot script which you can use to help you if you go down this route.