Hidden colours on objects

[Dragonwalker Art]

Hello all.
Lately I have been having some issues that I have never encountered before working the same way that I have always worked in Illustrator.
Sometimes I will use a different colour for a line while I work on it so that I can easily differentiate it and then change it to the required colour later. I think that sometimes I do this for a whole group of lines and so to recolour them I may select the group or even the layer to get them all and then either use the dropper tool so they match the others or change it manually in the color picker.
But now I am having difficulty where I may change the colour but then it will change visually but will still look the old colour when looking at the swatch on the left. It is so messy to fix it that it has been difficult to find out exactly what has been going on and pinpoint the issue and I cannot replicate it when I try (not sure if colouring the layer effect by accident but I try all that with often no effect. 
Saying that, the design I am working on should only have three colours (a certain grey, white and then Rich Black). Sometimes a 0 0 0 100 sneaks in instead of the RB so to be sure I went to recolor artwork to make sure the only colours in the image are the ones I needed and there is also red. None of the lines appear red so it is hard for me to 'select same' to find out where this colour is coming from.
Does anyone else suddenly have this issue and also is there a way of finding what objects are giving this colur reading without having to select one to 'select same'?

Thank you so much.

[Monika Gause]

I'm not quiote sure what your issue is about.

Are you talking about colors that are appearing out of nowhere? In that case you might have multiple strokes or fils applied to objects. Here's how to find them: https://www.youtube.com/watch?v=YZooJyG2UT4 

Or is this about inks appearing in your colors, then maybe you are going to and from CMYK to RGB and back.

[Dragonwalker Art]

Thank you for your timely response.

In regards to changing colour settings for the document. No, I am staying in CMYK mode for print.

I definitely think I have multiple fills etc. added, but it is strange that this never happened to me before recently. The thing is the video shows a situation where she knows where the issue is but in my case after just going layer to layer it was actually a small stray point that was red. 
I could have just changed the red to black but I wanted to know where it was but it was so small it wouldn't have been visible and it could also have been under another line for example.

I really wish that Adobe would add a feature under the Select options to be able to select objects of a particular colour by adding the colour code rather than having to select one of the same first, which in this instance was not possible.

[Monika Gause · Accepted solution]

The way to use the select menu is to create an object, apply the color you search and then select same. Or use the magic wand tool ,which you can use to select similar . Double click the magic wand to make the options appear.

[Dragonwalker Art]

How on earth did I not think of doing that!!! Thank you!!!

[Monika Gause]

You're welcome!