If you have a MAC delimited with hyphens:

xx-xx-xx-xx-xx-xx

You can convert it to use colons using sed:

echo xx-xx-xx-xx-xx-xx | sed 's/-/:/g'

Which will output as:

xx:xx:xx:xx:xx:xx

Anything can be replaced:

echo xx-xx-xx-xx-xx-xx | sed 's/-/%/g'

Would output:

xx%xx%xx%xx%xx%xx