To change an Elf EMS or ROM Mapper memory page from the memory dump tab use the 'EMS / ROM Map' field (hexadecimal values 0 to 1F, see lower yellow ellipse). EMS pages are connected from address hex 8000-BFFF and when shown the address will have the same colour as the 'EMS / ROM Map' text.
To change an Elf memory pager from the debugger use the 'Pager' fields (switchable 4K page, orange ellipse: values 0 to F, page, magenta ellipse: values 0 to FF). Memory pager pages are connected from address hex 1000 to hex FFFF in blocks of 4K. Page 0 is always connected from address 0 to hex FFF. The switchable 4K page is indicated by the first field (orange ellipse) and the selected pager by the second field (magenta ellipse).
The address of the selected switchable Pager will have the same colour as the 'Pager' text. So if switchable 4K page 1 is selected address hex 1000 to hex 1FFF will be shown in the pager colour, if page 2 is selected 2000-2FFF will be shown in the pager colour etc.