Remember this Mat #34 from here?
Marilee left a comment that I have three colour choices to proceed with this doily - green, white or yellow.
I have a ball of solid yellow that I think matches one of the colours of the HDT of the doily.
But the HDT that I used for the doily was marked size 30 and this yellow ball of thread is size 40. However, when I feel both threads with my fingers, I think they are about the same size.
From experience, I know that sometimes the thickness of thread show a difference even though the labels say that they are of the same size. So, I did the number-of-rolls-round-a-pen test with these two thread to find out if they are of equal thickness.
I roll one thread 20 times round a pencil, and push the thread so that the strands lie side by side without actually squeezing them up and do the same with the other thread round a pen (don't have another pencil handy). Putting them side-by-side like this, I can see that the thickness of the 20 strands of thread is about equal, the yellow solid on the left and the HDT on the right.
I think it is safe for me to use the yellow solid to continue with the doily.