I have entered the numbers 1-40 in a
block range of cells, say Column E1:E40. If I enter a number down
column A that matches any number from 1-40 I would like the
corresponding number in column E to change colour in some way. Is this
possible?

One way is to select E1:E40 and use:

Format Conditional Formatting Formula is

=COUNTIF(A:A,E1)0