Wrong text size and colors

I am hoping to find some answers here before I give up.

We have Version 5 of OmniGraffle. I am using it to design screens for a cloud based software.

Here are my 2 problems:

  1. Text size. For example, I create some text in OmniGraffle and give it a size of 12. I export my page as PNG with the settings “Size 100%” and “Bitmap resolution 72 DPI”. I open the PNG in Photoshop and measure the size of the text. It is not 12 pixels, it’s 9 pixels. (See attached screenshot)

  2. Colors. I draw a rectangle in OmniGraffle and give it the RGB color “222 34 61”. I export the page using PNG. I open the page in Photoshop and check the color, and it’s not the same: “231 60 110”. (See attached screenshot)

What am I doing wrong? I need a software that can create accurate PNG screens with correct text sizes and colors.

Thanks for your help!