Great Britain Philatelic Society

hi,everyone.here is a great britain queen elizabeth windsor castle five pound used stamp.i can see there are 3 colour shades keep changing around on the symbol of the stamp.the colour shades change from green to gold and then gold to pink colour shades underneath the bride light.the colour shades keep changing around just like the chameleon.normally i see is in gold colour shade on the symbol.is this normal for the stamp?if its not,what caused this happend?any special value?

What you have is Stanley Gibbons catalogue number 1614. The Queen's head is printed in optically variable ink which changes color from gold to green when viewed at different angles. It can also be found on the £1, £1.50 and £3 values.