Change theme colors of converted excel spreadsheet?

I’m using this calendar Monthly Calendar with Holidays for Excel

Currently I’m trying to figure out how to change the colors so it looks like what will print (printer is in black and white/greyscale).

Calc does have spreadsheet themes but it changes the colours for specific styles.

  1. Shift select sheets 1 - 12. All 12 sheet tabs should show as being selected
  2. In sheet 1, click on cell A4 and make a note of Font, style and size, that is Arial Regular 48
  3. In Cell styles in the style pane in the sidebar, double-click Heading 1 to apply the style to cell A4 in all the 12 sheets
  4. Using direct formatting, set the font, style and size back to that noted.
  5. Select cells A6:N6 and double click Heading 2 to apply that cell style. Centre the text vertically
  6. Save as [myFileName].ods
  7. Click the Help tab to deselect all and then click sheet 1 to see the effects
  8. click Format > Spreadsheet theme. In the dialogue, click on different themes to see the effects. Click Cancel to leave without making changes or OK to apply a theme.

If you don’t like the themes, you can right click the style Heading 1 and select Edit style,

  1. change the font, style and size in the font tab
  2. change the font colour in the Font Effects tab.
    Right click the style Heading 2 and select Edit style,
  3. change the background colour in the Background tab.
  4. Set alignment Horizontal to Centre and Vertical to Middle in the Alignment tab
  5. Set the Cell format to DDDD in the Numbers tab

After that you can just change the colours in the two styles.
monthly-calendar-with-holidaysEA116071.ods (121.9 KB)