understanding normal and order-only prerequisites

#edit: don't copy highlighted text, use 'raw paste data' textbox

MAKEFLAGS +=--no-print-directory -Rr

c_target              = "\033[01;31m"
c_requisite_normal    = "\033[01;32m"
c_requisite_orderonly = "\033[01;33m"
c_reset               = "\033[00m"

T=a b c d e f g
.PHONY: $(T)
$(T):
    @echo \
$(c_target) '>' $@ \
$(c_requisite_normal)$(if $+,':' $+) \
$(c_requisite_orderonly)$(if $PIPE>,'|' $PIPE>) \
$(c_reset)

.DEFAULT: a
d: g
c: f
a: b c | d e