VyoS uses VRF-lite meaning it acts on the interface addresses along with a routing table connected to each interface. That is “proper” namespace separation is missing (if you compare VRF with how for example Arista EOS is doing this).
So Im thinking wouldnt something like this then work for you?
eth0: vrf: RED: 10.0.0.1/24
eth1: vrf: BLUE: 10.1.0.1/24
set vrf name RED protocols static route x.x.x.x/yy interface eth1
or:
set vrf name RED protocols static route x.x.x.x/yy next-hop <ip of BLUE>
Eventually you might need to add:
set vrf bind-to-all
At least in 2021 the syntax of defining a next-hop being vrf seems to have existed - dunno what happend to that: