solos turning green & affecting control of solo & mutes

Recently when I've opened a song some of the solo buttons are now green not the normal yellow.

There seems to be unusual responses to mute and solo functions.

This is not present in other projects or songs just some.

I created a new channel under the one with a green solo & copied & pasted the file into the new track.

The solo on the newly created track is it's normal yellow colour.

What have I done to induce this new oddity?

Is this some form of automation I have somehow by accident?

How do I change things back or deactivate what I have done & prevent it happening again?

S1 V2 producer windows 7

Thanks in advance

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