Black and White first page of each merged PDF

[metaesthetic]

When viewing some merged PDFs and viewing them in Adobe Acrobat Reader DC or Adobe Acrobat Pro DC, the first pages of each individual PDF are black and white whereas the rest of the pages are in color. This does not happen in Mac Preview or in the Chrome browser when viewing the PDFs. The Individual PDFs look fine in Acrobat but after using pdfmerge (1.0.4 and 1.0.6) and saving the file, only the first page of multiple-page PDFs within the merged PDFs are black and white (for single page PDFs, the first and only pages are still in color). I tried to remove any potential CSS conflicts that were used when creating the PDFs in case there was some latent code but that doesn't seem to help. Anyone else encountering this issue? Thanks.
all-alloys (1).pdf
wrought-coppers.pdf
wrought-high-coppers.pdf

[dmaphy]

Unfortunately I'm unable to reproduce this issue as I don't have any installations of windows and/or Acrobat tools. Evince on Linux doesn't have any issues with the documents as far as I can see.