I'm convinced it's passion's pledge (a) because it rhymes and (b) because it makes sense - Passion play doesn't mean anything to me, Passion's pledge does.

I've always heard the other lines as :

I gave her gifts of the mind, I gave her the secret sign,
That's known to the artist who has seen the true gods of sound and stone,
And words and tint, I did not stint for I gave her poems to say ...

The "words and tint" seem to work as either the end of the previous line or the beginning of the next one, ie I didn't stint on the words or the tint when I was writing the poems for her.

I learned this mainly from Luke Kelly's singing, but I'm not 100% sure I have Luke's words verbatim,