Suid Africa Colour Missing?

Hi all
I found these stamps and the missing colours stood out as unusual.
Would appreciate any help and advice as to whether known errors.
Thankyou

I don't do much with South Africa, but the first 2 appear to be Scott 98 and one of Scott 23/33/45.
Second pair are also 2 different catalog numbers.
Many stamps in "workhorse" series get reworked and reissued in variants over a span of years. They are not errors. If you are using a Scott catalog, they do a good job under the first instance of a design to note later catalog numbers of similar-appearing variants.

John
Thankyou - very much appreciated
I'll look it up

Looks like the 1st stamp is a redrawn sg104/105?

The springbok stamp on the left is a 1943 coil, the stamp on the right is one of the many variants of the sheet stamp issued between 1926-1953.
The Groot Constantia stamp on the left was issued on 31.05.1961, and occurs with two watermark varieties (same watermark but different orientations; left and right). It is the first printing of the value in the 2nd definitive series of the Republic of South Africa and was reprinted several times over the years until 1970 of which the stamp on the right is an example of.

Thankyou
Appreciate your help