Thanks for contacting support.
I have tested the scenario of PDF to PNG conversion using latest release of Aspose.Pdf for Java and have managed to reproduce the issues that colors and pictures are garbled in resultant PNG files. For the sake of correction, I have separately logged them in our issue tracking system.
PDFNEWJAVA-34950 - myWorld+Activity.pdf
PDFNEWJAVA-34951 - Professional+Development+Essays.pdf
We will further look into the details of these issues and will keep you posted with our findings. We are sorry for this inconvenience.
PS, Can you please share the resource file for PREVIEW_myWorld+Activity_1.Png image which you are shared, so that we can also test this scenario.