We are very happy that the Arc theme from Horst3180 is standard issue on Solus when you install it. Arc has an blue accent colouring scheme. The colours can however not be changed (easily).
But we can install an Arc Red theme from github to have some variety.
Go to the github of Ultimate Solus and install the script :
Check out the red accents everywhere.
If you feel adventurous, you can learn about a script I developed to change Arc to any of the 16 million colours here.