Sign colours have stopped working

Up until yesterday 14/4/2021 I ways able to create coloured signs which were bright and looked lit up. I have tried to create further signs and now they are dull/dark even when using the cone method as I did previously. 

is this because of a update or has the way you create coloured sign suddenly changed? I use coloured signs as warnings were not to dig and for directional signs.

 

please help