Get a Bumblebee...
Why:
Bumblebees are double hets for pastel and spider. At both the spider and the separate pastel locus they have one mutant (pastel or spider respectively) and one of the corresponding normal versions of the same gene. So you know that between the two parents there was at least one copy of each gene and also between the two parents there was at least one normal copy of each gene. Most so far would be from spider X pastel but it would also be possible to create a bumblebee from bumblebee X normal and several other combination.
Bumblebees statistically can produce:
25% Spiders, 25% Pastels, 25% Bumblebees and 25% normals
This doesn't mean that 1 in 4 will be bees, it just means that statistically speaking you have those odds, of course they could all be normals or all pastels or all spiders or all bees... catch my drift?
This example gives you an idea if you were to just pickup one male morph and wanted to produce many variant mutations spread over many females.
PS: Again be careful overbreeding just one male can and will lead to hemi-peen infections ultimately retiring that male for the season if you over breed it to many females in a cycle. I just want to say this is not something I do nor will ever recommend to anyway.