The first part of the exercise involved painting a small square several times and then painting another square round it in a colour close to it on the spectrum. Looking at this top row of squares you can see that they are all blending together, the two at the far right perhaps having a little more distinction between colours as I go further away from the colour on the colour wheel.
Next we are asked to use complimentary colours, those opposite each other on the wheel. Here they have the effect of enhancing each other.
The final part of the exercise, choosing complimentary colours again, but putting a neutral grey right next to them. Here the neutral takes on a slightly different shade relative to which colour it is with -simultaneous contrast.