Select your row or cell
Go to table menu
Cell options...strokes and fills
Set fill to none
Shorter:
Select your row or cell
'x' to switch between stroke or fill
Click on your colour swatch ('none' in your case)
If I'm overinterpreting then indeed, there doesn't seem to be a question to ask/answer here. If the table cells have no fill the picture will show through.
Dave
I place a picture on a page.
I create a separate text frame with no fill. I insert a table into that frame. I enter data into the table.
I put the text frame that contains the table over the picture. You see the picture under the table.
What am I missing here?
It works on the whole frame and everything in it.
So, to get a transparent background for a table that doesn't also affect the text in the cells in the table, you need to create a separate frame and put it behind the table. Let the fill of that frame serve as the background of your table (if you want different rows in the table to have different colored backgrounds then it gets even more complicated).
One way to do this is to use an inline graphic. Draw the frame the right size and put it in a paragraph of its own immediately before the table. Give the paragraph a small fixed leading (could even be zero) and drag the frame down as far as it will go so it sits behind the table.
Getting the frame to be exactly the right size and exactly the right offset from its baseline can be fiddly and is probably best done with a script.
Dave
In that case, scrub what I said above. Give that cell a fill of none. Now make a rectangle the same size as the cell and make it a transparent blue. Cut and paste it into the cell as an inline frame within the text of the cell. Again, you might have to fiddle to get things just right. The insets of the cell will need to be zero.
Dave
Dave, thanks for the comment, it support the other way I was thinking on accomlishing this per cell.