Question about colors and army painting

Can my sister squads all be the same color scheme (white/green/gold) but then have my other units (Seraphim/Rhino/Castigator) be a different color scheme (Black/Green/Silver)?

I was thinking all my basic units would be the first color scheme then the specialized units be the second color scheme, but I want to know if this tpye of army painting style is frowned upon.