I've migrated to Angular Material 15 and found out, that background in my tables has different color. I've come to Material site, went to table component and changed background color for row there. Also, made this for another version of material. Here are the results:
As you can see, background has same color value, but looks like another color. I thought, that in 14 version they had some opacity set on the table, but didn't found that. And the trouble reproduces only when setting rgba. rgb or hex works fine.