google spreadsheet - If column includes a certain value, turn top cell red -

i want function can check 1 column value , if @ least 1 value found top cell should become red. intent visualize function of top cell in said column:

if cell in column "a" = "x" cellbgcolor = red else cellbgcolor=white 

i don't mind doing in 2 steps, i.e. if value found type "x" in cell , use conditional formatting paint cell.

please try:

=match("x",a:a,0)   

with applies to range: a1.