How to have monocrome "Dark Blue" rather than "Black" for the following operation?

Dear illustrious List Maintainers and Senior Members, GraphicsMagick Help,

I am very new to graphicsmagick.

I have searched the list with the string: 1-bit image "single color"
"small file size" Image  -Large -mask

2053 posts were found. Beyond me to skim through all posts based on
the subject line.

So I apologise if there is indeed a already available reply for the
question asked here.

Assuming that I have a formatted text only pdf file with the name
"name.pdf", I can use the following code to batch-convert all the
pages as one monocrome black-white image for each page with the
following command-line:

convert  -density 100 name.pdf -colorspace Gray  name-%03d.jpg

If I want a Dark Blue text with a transparent background for each
pages, instead of Black, how should the command line be altered?

I checked the man page for the colorspace choices. But I can't make
out how to set a single colour for the monocrome jpeg image?

The identifier for Dark Blue:
PMS: 3591 C
Hex Color: #06038D;
RGB: (3,37,126)
CMYK: (100,87,0,25)

Eager for your advice.

Best wishes.
Rajib B
An Open Source Software enthusiast and user